Cycloaliphatic unsaturated ketones as odor and taste modifying agents in tobacco products

ABSTRACT

New cycloaliphatic unsaturated ketones used as flavoring and taste modifying agents in tobacco products.

This is a division, of application Ser. No. 676,505, filed Apr. 13,1976, now abandoned which in turn is a divisional of application Ser.No. 503,738, filed Sept. 6, 1974, and which has since matured into U.S.Pat. No. 3,975,310, which in turn is a divisional of application Ser.No. 35,594, which was filed on May 7, 1970, which was subsequentlyabandoned in favor of the continued prosecution in Ser. No. 523,743,filed Nov. 14, 1974, which matured into U.S. Pat. No. 3,931,326, whichapplication Ser. No. 35,594, is a Continuation-in-Part of Ser. No.774,179, which was filed on Nov. 7, 1968, which is now abandoned.

SUMMARY OF THE INVENTION

The invention relates to a new class of cycloaliphatic unsaturatedketones having the formula ##STR1## containing one double bond inposition 2'- or 3'- of the acyl side-chain and either one double bond inposition 1- or 2- as shown in the above formula, the double bond in the2 position can be either in the cycle of the side chain, or twoconjugated double bonds in positions 1- and 3- of the cycle, the doublebonds being represented by dotted lines, and wherein n is zero or 1, R¹,R² and R³ represent hydrogen or one of them a lower alkyl radical, suchas methyl or ethyl, and the others hydrogen, and R⁴, R⁵, R⁶ and R₇represent hydrogen or one of them a lower alkyl radical, such as methylor ethyl, and the others hydrogen.

The invention also relates to methods for the preparation of compoundsI, of some of the intermediates used in their preparation and some oftheir derivatives and to the use of said compounds as perfuming andodour-modifying agents in the manufacture of perfumes and perfumedproducts, and as flavouring and taste-modifying agents in themanufacture of artificial flavours for foodstuffs, beverages, animalfeeds, pharmaceuticals and tobacco.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The compounds of the invention have particularly interesting andvaluable organoleptic properties and, consequently, they are useful asfragrances in the perfume industry, as ingredients for the preparationof artificial flavours and as flavour additives in foodstuffs, animalfeeds, beverages, pharmaceutical preparations and tobacco products.

The term "foodstuff" is used in this specification in its broadest senseand is meant to include also products such as coffee, tea and cocoa. Inparticular, the new ketones and some of their intermediates can be usedas odoriferous ingredients in concentrated or diluted perfumes and inperfumed products such as soaps, detergents, cosmetic products, waxesand any other products which may be perfumed to make them commerciallymore attractive.

Furthermore, the new compounds are very useful as ingredients in thepreparation of artificial essential oils such as jasmin oil, geraniumBourbon oil, rose oil and others.

The compounds of the invention increase the power and the diffusionability of perfume compositions and impart to them a natural richness.

The compounds of the invention possess also very interesting flavouringproperties. Depending on the nature of the products to which they areadded, they will develop fruity, herb-like, winy, woody, floral or waxyflavour notes or any combinations of these flavour notes. In someinstances they will impart to products a red berry-like flavour and canbe used for improving the taste and aroma of artificial strawberry,cranberry, cherry or red-currant flavour compositions and the like.Surprisingly, the new ketones can even be used for enhancing the tasteand flavour of such products as honey and red wines.

The proportions in which the new compounds can be used to producedesirable odoriferous effects vary within wide limits. In thepreparation of perfume compositions, for instance, interesting effectscan be obtained with proportions as low as about 100 ppm to about 5% ofthe total weight of a perfume composition. Depending on the odoriferouseffects wanted, the proportions of the ketones can be increased to about10% or even more.

When the new ketones are used as flavouring agents or additives formodifying the organoleptic properties of foodstuffs, animal feeds,beverages, pharmaceutical preparations and tobacco products, the newcompounds can be used in proportions which, again, vary within widelimits.

Interesting flavouring effects, for instance, can be achieved by usingthe compounds of the invention in proportions from 0.1 to 10 ppm basedon the weight of the products to be flavoured. However, theseproportions can be increased beyond 10 ppm up to about 100 ppm in orderto achieve special flavouring effects. In the preparation of flavouringcompositions by admixing the new compounds to other aromatics, the saidcompounds can be used, for example, in proportions of about 0.1% toabout 15% of the total weight of the flavouring composition. In manycases average proportions of about 1 to 10% by weight will give thedesired results.

It is to be understood that the proportions given above are in no wayabsolute values and that higher or lower concentrations of the newcompounds may be used depending on the specific odoriferous orflavouring effects to be developed.

According to the invention, the methods of preparation of the compoundsof formula I are either of general nature or of more specific type.

According to the invention, a general method for the preparation ofcompounds of formula ##STR2## containing either one double bond inposition 1- or 2- or two conjugated double bonds in positions 1- and 3-of the cycle, the double bonds being represented by dotted lines, andwherein R¹, R₂ and R³ represent hydrogen or one of them a lower alkylradical, such as methyl or ethyl, and the others hydrogen, and R⁴, R⁵,R⁶ and R⁷ represent hydrogen or one of them a lower alkyl radical, forexample methyl or ethyl, and the others hydrogen, comprises acylatingorgano-metallic propene derivatives having the formula ##STR3## whereinthe symbols R¹, R² and R³ have the same meaning as above and MErepresents a metallic function such as Li, Zn, Cd and Mg-halogen, withcyclogeranoyl or safranyl derivatives having the formula ##STR4##wherein the dotted lines and the symbols R⁴, R⁵, R⁶ and R⁷ have the samemeaning as above and wherein the symbol X represents a leaving groupsuch as halogen, O-alkyl, O-aryl, O-CO-aryl, O-CO-alkyl.

A preferred mode of operation consists in using, as cyclogeranoylderivatives, geranoyl halogenides such as, for instance, chlorides,bromides or iodides or geraniate derivatives such as methyl, ethyl orlithium geraniate. The cyclogeranoyl and safranyl derivatives used inthe above mentioned process can be synthesized according to differentmethods, some of which are described hereinafter. For instance,

(1) The cyclogeranoyl derivatives of structure α- and β - can besynthesized from the corresponding cyclogeranic acids by usual methods.The cyclogeranic acids may be obtained from the corresponding citralderivatives according to known methods [c.f.: Gildemeister & Hoffmann,Die Aetherischen Oele, III d, pp. 137-138, Akademie-Verlag, Berlin(1966)]. The process for the preparation of the cyclogeranoylderivatives of structure α- and β- can be illustrated by the followingscheme A wherein the dotted lines and the symbols R have the samemeaning as above. ##STR5##

(2) The cyclogeranoyl derivatives of structure α-, β- can also beobtained by cyclisation of the corresponding citral derivatives [e.g.cf.: Bedoukian, Perfumery and Flavoring Synthetics, Elsevier, New York(1967)], whereas the cyclogeranoyl derivatives of structure γ- areobtained by isomerization of β-cyclocitrals. The aldehydic group ofcyclocitrals is oxidised to --COOH and finally this latter istransformed into --COX by the usual means. Scheme B illustrates thisprocess. The dotted lines and the symbols R have the same meaning asabove. ##STR6##

(3) The cyclogeranoyl derivatives of structure γ-, where X= O-alkyl, canbe prepared according to Helv. Chim. Acta. 41, 1359 (1958) from anα-alkoxycarbonyl derivative of cyclohexanone. By condensation of thesederivatives with an ethyl haloacetate in the presence of zinc a diesteris obtained which, after dehydration, partial saponification andmonodecarboxylation, gives the desired γ-compounds. This process isillustrated in Scheme C hereinafter. The dotted lines and the symbols Rhave the same meaning as above. ##STR7## The α-alkoxycarbonylderivatives of cyclohexanone may be obtained according to Helv. Chim.Acta 35, 1753 (1952) from methylheptenone.

(4) The safranyl derivatives used in the process of the presentinvention can be obtained simply by dehydrogenating the correspondingβ-cyclogeranoyl derivatives as follows. The substituents R have the samemeaning as above.

Scheme D: ##STR8## The dehydrogenation may be carried out in the sameway as that described for one of the process of the invention whichconsists in converting compound Iα and Iβ and Iδ. This process will bedescribed hereafter.

According to the invention, a method for the preparation of ketones offormula ##STR9## containing one double bond in position 2'- or 3'- ofthe acyl side-chain and one double bond in position 1- (structure β-) or2- (structure α-, endocyclic double bond; structure γ-, exocyclic doublebond) of the cycle, the double bonds being represented by dotted lines,and wherein n is zero or 1, R¹, R² and R³ represent hydrogen or one ofthem a lower alkyl radical such as methyl or ethyl, and the othershydrogen, and R⁴, R⁵, R⁶ and R⁷ represent hydrogen or one of them alower alkyl radical, such as methyl or ethyl, and the others hydrogen,comprises oxidising an alcohol of formula ##STR10## wherein the dottedlines and the symbols R have the same meaning as those of formula I.Silver carbonate in presence of diatomaceous earth, oxygen-containingderivatives of a transition element such as chromium, manganese ornickel, pure or atmospheric gaseous oxygen in presence of activators,such as, for example free radicals initiators, can be used as oxidisingagents. Chromium trioxide and manganese dioxide are preferably used [seefor example, J. Org. Chem. 26, 4814 (1961)]. MnO₂ is a cheap oxidisingagent which can be used at room temperature in an inert solvent such aspentane and hexane.

When it is used to convert V to I, the geometric isomerism of thematerial being oxidised (cis- or trans- alcohols V or mixture thereof)remains practically unchanged. When CrO₃ is used, preferably in thepresence of an organic base such as pyridine, the ketone resulting fromeither the cis- or the trans-alcohols V has the geometry trans-. Thestarting compounds V which possess interesting organoleptic propertiesand, consequently, can be advantageously used in the perfume industry,can be prepared according to usual methods by the addition to α-, β- orγ-cyclocitrals of an organo-metallic derivative having the formula##STR11## containing one double bond in position 1'- or 2'-, the doublebond being represented by the dotted lines, and wherein ME represents ametallic function such as, for instance, Li or BrMg, R¹, R² and R³ havethe same meaning as above and n is zero or 1, and subsequent hydrolysisof the addition product.

The above process is illustrated by scheme E herebelow, wherein thedotted lines and the symbols R have the same meaning as above. ##STR12##The α-, β- and γ-cyclocitrals can be prepared from citral derivatives asindicated in scheme B (see above) and schemes F and G will illustrate afew examples of reactions for the preparation of such starting citralderivatives. In these schemes the symbols R have the same meaning asindicated above, ME represents a metallic function and a indicates anaddition reaction of an organo-metallic reactant on a ketone [see forexample, D. J. Cram and G. S. Hammond, Organic Chemistry, McGraw-Hill,New York (1959) p. 294]

Scheme F ##STR13##

Scheme C:

b: Carrol reaction [see for example J. Chem. Soc. pp. 704, 1266 (1940);p. 507 (1941)]

c: Reactions for the conversion of methylheptenones to the correspondingcitrals [see for example Bedoukian, Perfumery and Flavoring Synthetics,Elsevier, New York (1967), p. 102-103] ##STR14## wherein the symbol R²represents hydrogen, R¹ and R³ represent hydrogen or one of them a loweralkyl radical, such as methyl or ethyl, and the other hydrogen, and R⁴,R⁵, R⁶ and R⁷ have the same meaning as above, can be prepared byisomerisation and simultaneous reduction of an epoxide having theformula ##STR15## wherein the R's have the same meaning as above [seeTetrahedron 19, 1091 (1963) and J. Org.Chem. 26, 3615 (1961)].

According to the invention, the ketones of formula I α- and I β-,wherein the double bond of the acyl side-chain is in position 2'-, areprepared by cyclising, by means of an acidic cyclising agent, a "pseudo"-ketone of formula ##STR16## wherein the R's ahave the same meaning asin formula I. The cyclisation can be carried out under the sameconditions used for cyclising the 1,5-dieno compounds, for example forcyclising citral to cyclocitral or geranic acid to cyclogeranic acid[see for example, P. Z. Bedoukian, Perfumery and Flavoring Synthetics,Elsevier, New York (1967)].

When cyclising agents such as proton acids are used to effect thecyclisation the resulting ketone I possesses generally the structure -β,that is to say with the double bond in the ring conjugated with theCO-group (position 1- of the ring). When cyclising agents such as Lewisacids are used in the cyclisation, for instance boron trifluoroetherateor SnCl₄, the resulting ketone I possesses generally the structure α-,that is to say with the double bond in position 2- of the ring. Thecyclisation is preferably carried out by means of SnCl₄ in an inertsolvent such as benzene or toluene.

In the above mentioned process, the starting "pseudo"-ketones, which arenew odoriferous compounds and can be advantageously used in the perfumeindustry, can be easily obtained by reacting a citral derivative (seescheme G) with an organo-metallic derivative of propene (see formula IIIabove), under conditions analogous to those described for thepreparation of alcohols V, and subsequent oxidation of the resultingalcohol with an oxidising agent. Said oxidation can be carried out bymeans of the same oxidising agents and under reaction conditionsanalogous to those used for the oxidation of the alcohols having formulaV.

The "pseudo"-ketones VI can also be prepared from methylheptenonederivatives (cf. scheme G) according to the process shown in scheme Hhereinbelow wherein the symbols R have the same meaning as above.

Scheme H: ##STR17##

According to the invention a method for the preparation of compoundshaving the formula ##STR18## containing one double bond in position 1-or 2- of the cycle, the double bonds being represented by dotted lines,wherein R¹, R², and R³ represent hydrogen or R¹ a lower alkyl radical,such as methyl or ethyl, and the others hydrogen, and R⁴, R⁵, R⁶ and R⁷represent hydrogen or one of them a lower alkyl radical, such as methylor ethyl, and the others hydrogen, comprises partially hydrogenating thetriple bond of an acetylenic ketone having the formula ##STR19## whereinthe dotted lines and the symbols R have the same meaning as in formulaI. The partial hydrogenation can be performed in the presence of aLindlar type catalyst (deactivated Pd/C catalyst, see Helv. Chim. Acta35, 446 (1952)) according to usual methods. The ketones I α-a and I β-aresulting from the above partial hydrogenation have the configurationcis-. The corresponding transisomers are prepared according to theinvention by isomerisation with an acid in an inert solvent. Acids whichcan be used for carrying out the above isomerisation comprise protonacids, such as those ordinarily used to produce enolisation of ketones,for instance p-toluenesulfonic acid, hydrochloric acid andtrifluoroacetic acid. Lewis acids, such as for instance borontrifluoride or iodine, can also be used. The isomerisation is bestcarried out in an inert solvent such as an aromatic hydrocarbon, forexample benzene or toluene, an aliphatic or cycloaliphatic hydrocarbon,e.g. heptane or cyclohexane, or an ether, e.g. monoglyme, digylme ordioxan. The temperature at which the isomerisation can be carried out isnot critical. For instance, the isomerisation can be carried out bymixing the substance to be isomerised together with the solvent and acatalytic amount of the acidic isomerising agent and allowing themixture to stand at room temperature for several hours, e.g. 12 hours.At lower temperature the reaction time may increase considerably. Attemperatures higher than the room temperature the reaction time may beshortened. However, above 100° C. unwanted side reactions may occur andit is preferable to carry out the isomerisation below 100° C.

The acetylenic ketones VII which are used as starting materials in theabove process are themselves odoriferous new compounds which can be usedin the perfume industry. They possess valuable floral fragrances. Theycan be prepared by a method which comprises reacting α- orβ-cyclocitrals with organo-metallic derivatives of propyne, subsequentlyhydrolysing the reaction products to acetylenic alcohols and oxidisingthe latter to the ketones. VII.

This method can be illustrated by scheme I underneath. ##STR20##

In scheme I the dotted lines and the symbols R have the same meaning asabove. The symbol ME represents a metal function such as those commonlyfound in organometallic compounds, for instance alkali metals, mercury,zinc, cadmium and magnesium. In cases where ME represents a divalentmetal, i.e. for instance Mg, the second valence bond can be linked to anegative substituent such as for instance Br, Cl or I. For the oxidationof the acetylenic alcohols to ketones VII, the same oxidising agentsused for the oxidation of alcohols V to ketones I can be used undersimilar conditions. Good results are obtained by carrying out theoxidation with MnO₂ in a cheap inert solvent such as hexane, cyclohexaneor petroleum ether.

The acetylenic ketones of formula VII can also be prepared by the directacylation, according to usual procedures, or organo-metallic propynederivatives of formula

    ME--C.tbd.C--CH.sub.2 R.sup.1

wherein ME represents a metallic function such as for instance Li, Na orK with cyclogeranoyl derivatives having the formula IV α- or IV β- (seescheme A above).

According to the invention, a method for the preparation of compoundshaving the formula ##STR21## containing one double bond in position 1-or 2- of the cycle, the double bond being represented by dotted lines,wherein R¹, R² and R³ represent hydrogen or one of them a lower alkylradical, such as methyl or ethyl, and the others hydrogen, and R⁴, R⁵,R⁶ and R⁷ represent hydrogen or one of them a lower alkyl radical, suchas methyl or ethyl, and the others hydrogen, comprises isomerisingcompounds having the formula ##STR22## wherein the dotted lines and thesymbols R have the same meaning as above, by means of an acidic or basicisomerising agent or by means of heat. As acidic isomerising agent astrong mineral or organic acid, such as for instance sulphuric acid,phosphoric acid, gaseous hydrochloric acid, perchloric acid,p-toluensulfonic acid and trifluoracetic acid can be used.p-Toluensulfonic acid is preferably used. The isomerisation by means ofan acidic isomerising agent can be carried out in an organic solvent.For instance, most of the commonly used organic solvents such asaliphatic cycloaliphatic hydrocarbons, aromatic hydrocarbons,chlorinated hydrocarbons or esters and ethers can be conveniently used.Benzene is preferably used.

As basic isomerising agent an alkali, an alkali-buffer or an organicbase can be used.

According to the invention a method for the preparation of compoundshaving the formula ##STR23## containing one double bond in position 2'-or 3'- of the acyl side-chain, the double bond being represented bydotted lines, wherein n is zero or 1, R¹, R² and R³ represent hydrogenor one of them a lower alkyl radical, such as methyl or ethyl, and theothers hydrogen, and R⁴, R⁵, R⁶ and R⁷ represent hydrogen or one of thema lower alkyl radical, such as methyl or ethyl, and the others hydrogen,comprises dehydrogenating the compounds of formula ##STR24## wherein thedotted lines and the symbols R have the same meaning as above.

The dehydrogenation can be carried out by halogenating the cyclohexenicring in the allylic position and subsequently dehydrohalogenating theproduct of halogenation. As halogenating agents, commonly knownhalogenating reactants of the allylic position such as for instance,haloamides, for example N-bromosuccinimide, N-bromoacetamide,N-dimethyldibromohydantoin and their chlorinated analogues can be used.

According to the usual procedure, N-bromosuccinimide is preferably used[see Chem. Rev. 63, 21 (1963)].

The halogenation in the allylic position can be carried out in an inertsolvent at a mild temperature. For instance, a chlorinated solvent suchas CCl₄, CHCl₃, CH₂ Cl₂, dichloroethane, tetrachloroethane andtrichloroethylene or a mixture of said solvents and temperature betweenabout 20° and 100° can be considered as convenient. It is possible tooperate at higher temperatures, but the course of the reaction becomesdifficult to follow. Preferably, the allylic halogenation is carried outin a mixture of CCl₄ and CH₂ Cl₂ and CHCl₃ at a temperature comprisedbetween 40° and 70° C.

The presence in the reaction mixture of an initiator such asα-α'-azo-bis-isobutyronitrile or benzoyl peroxide or the use of actinicradiations is advantageous. In such case in fact, the initial reactiontemperature can be appreciably lower than in the absence of such aninitiator; an easier control of the course of the reaction is thuspossible.

The dehydrohalogenation of the resulting halogenated product of theabove reaction can be carried out without isolation and/or previouspurification of said halogenated product and can be promoted by organicbases such as for instance tertiary amines. As tertiary aminespiperidine, morpholine, tributylamine, diethylaniline anddimethylaniline can be used. Preferably, diethylaniline is used owing toits low volatility but other tertiary amines can be equally effective.

The temperature of the dehydrohalogenation is comprised between 100° and150° C. However, it is possible to operate at temperatures below orabove these limits but at temperatures below 100° C. the reaction timemay become longer, whereas at temperatures above 150° C. the product mayundergo a partial decomposition.

According to the invention a method for the preparation of compoundshaving the formula ##STR25## wherein R¹, R₂ and R³ represent hydrogen orone of them a lower alkyl radical, such as methyl or ethyl, and theothers hydrogen and R⁴, R⁵, R⁶ and R⁷ represent hydrogen or one of thema lower alkyl radical, such as methyl or ethyl, and the others hydrogen,comprises treating with an acidic agent an epoxy-compound of formula##STR26## containing one double bond in position 2'- or 3'- of the acylside-chain, the double bond being represented by dotted lines, wherein nis zero or 1, and wherein the oxygen atom of the epoxide cycle is boundto the positions 1- and 2- or 2- and 3- of the cycle and the symbols Rhave the same meaning as above.

As acidic agents, mineral or organic acids such as, for instance,hydrochloric acid, phosphoric acid, sulphuric acid, p-toluensulfonicacid and trifluoracetic acid or acidic diatomaceous earth can be used.The reaction can be carried out in an organic solvent such as forexample benzene, toluene, tetrahydrofuran, dioxan or ethyl acetate at atemperature comprised between about 20° and about 100° C. Preferably,phosphoric acid in dioxan tetrahydrofuran is used and the reaction iscarried out at the boiling temperature of said solvents.

The above reaction proceeds through the formation of an hydroxyintermediate of formula ##STR27## containing one double bond in position2'- or 3'- of the acyl side-chain wherein the symbols R have the samemeaning as above, and wherein the OH-- radical is bound to position 1-,2- or 3- of the cycle. Compounds IX, such as2,6,6-trimethyl-1-hydroxy-1-crotonoyl-2-cyclohexene, are new and possessvery interesting organoleptic properties and are useful in the flavourand perfume industry.

According to another method of the invention, compounds of formula Iδ-aare prepared by oxidising, by means of one or more than one oxidisingagent, a compound of formula ##STR28## containing one double bond inposition 2'- or 3'- of the acyl side-chain and one double bond inposition 1- or 2- of the cycle, the double bonds being represented bydotted lines, wherein n is zero or 1 and wherein the symbols R have thesame meaning as in formula Iδ-a.

As oxidising agent, an oxygen containing derivative of an alkali metals,such as potassium chromate or bichromate, or of a transition element,such as chrome, manganese or nickel, can be used. The oxidation ispreferably carried out by CrO₃ in a mineral or organic acid.

The oxidation of compounds Vii to ketones Iδ-a can also be carried outby the successive use of at least two different oxidising agents suchas, for instance, a peracid and CrO₃. According to a preferred mode ofoperation, a peracid in a buffered hydrophobic solvent and an acidaqueous solution of CrO₃ are added successively to the alcohol Vii atroom temperature. In this process a peracide such peracetic acid,performique acid perbenzoic acid, perphtalic acid or m-chloroperbenzoicacid in a solvent such as, for instance, chloroform, methylene chloride,benzene or trichloroethylene in the presence of a buffer such as analkali acetate, can be used. Preferably, CrO₃ is then used in an aqueoussolution acidified with H₂ SO₄.

The above method can be summarised by scheme J hereinafter. ##STR29## Inthe above scheme J the dotted lines, the index n and the symbols R havethe same meaning as in formula VIIIi (see above).

According to the above described process, the epoxy intermediates arenot isolated; however, when required these epoxides, which are newodoriferous products and can be advantageously used in the perfume andflavour industry, are prepared according to the invention by epoxidisinga compound of formula ##STR30## wherein the dotted lines, the index nand the symbols R have the same meaning as above and X represents anoxygen or hydrogen, and an --OH group. As epoxidising agents the sameperacids described above for the oxidation of V ii can be used. Thereaction can be carried out in an analogous way.

The epoxy-ketones VIII i are obtained according to the invention byoxidation of compound VIII ii.

As oxidising agents, the reactants commonly known to oxidise a secondaryhydroxylic function to a ketonic function such as oxygen-containingderivatives of silver or of a transition element such as chrome,manganese or nickel, can be conveniently used.

An alkali bichromate in acidic solution is preferably used.

The compounds of general formula I possess in their side-chain a cis- ortrans- configuration. Some of the methods of the invention givegenerally mixtures in which the respective amounts of the two isomersvary within broad limits. As a general rule, for economic reasons themixtures obtained by one of the above process are used in the perfumeindustry without further purification or separation. However, ifnecessary the two isomeric forms can be separated by the usual methods,for instance, by column or vapour phase chromatography. Moreover,cis-isomers isomerise to the corresponding trans-isomers in the presenceof acids. By actinic radiations an equilibrium is established betweenthe two forms, in other words, by irradiating one or the other of thetwo isomers, a mixture, in which the amount ratio of the two isomers isconstant, will be formed. Such ratio will not change even if theradiation time is protracted.

It has been found that bicyclic compounds of formula ##STR31##containing either a six-membered saturated carbon cycle or an hexenicring wherein the double bond is in position 2-, the double bond beingrepresented by the dotted line, and wherein the symbols R¹ and R²represent hydrogen or one of them a lower alkyl radical, such as methylor ethyl, and the other hydrogen, and R³, R⁴, R⁵ and R⁶ representhydrogen or one of them a lower alkyl radical, such as methyl or ethyl,and the others hydrogen, and of formula ##STR32## wherein the symbols Rhave the same meaning as above, possess very valuable organolepticproperties and can be conveniently used in the perfume and flavourindustry.

According to a method of the invention, compounds X i are obtained bycyclising by means of an acidic or basic agent a compound of formula##STR33## containing one double bond in position 2'- or 3'- of the acylside-chain and containing either one double-bond in position 1- or twoconjugated double bends in positions 1- and 3- of the ring, the doublebonds being represented by the dotted lines, and wherein the index n iszero or 1 and the symbols R have the same meanings as in formula X i.

The cyclisation can be carried out by using as acidic agent either amineral or organic protonic acid, such as hydrochloric acid, phosphoricacid, sulphuric acid, acidic diatomaceous earth, p-toluensulfonic acidor trifluoracetic acid, or Lewis acids, such as BP₃, AlCl₃, SnCl₄ oriodine. It is possible to cyclise the compounds of formula XI tocompounds X i by dissolving the compounds to be cyclised in the presenceof the acidic agent in an inert organic solvent. Most of the solventscommonly used, such as aliphatic, cycloaliphatic or aromatichydrocarbons or esters and ethers can be conveniently used. Preferably,acidic diatomaceous earth in dioxan or tetrahydrofuran is used.

As basic agents strong inorganic bases, such as hydroxy-derivatives ofalkali metals, for example lithium, sodium or potassium hydroxides, ororganic bases, such as primary, secondary or tertiary amines, forexample diethylamine, triethylamine, n-propylamine, di-n-propylamine,tri-n-propylamine, n-butylamine, aniline, methylaniline,dimethylaniline, trimethylamine or diethylamine, can be used. Inaddition, said cyclisation can be carried out by means of usualnucleophilic reagents such as, for example, I⁻, SO₃ ⁻ or S₂ O₃ ⁻⁻.

The bicyclic ketone of formula ##STR34## is also prepared by oxidisingthe corresponding carbinol having the formula ##STR35## Compound XV canbe converted to Xa by means of the oxidising agents commonly used foroxidising a secondary alcohol in a ketone such as, for example,oxygen-containing derivatives of a transition metal such as chrome,manganese or nickel.

The starting carbinol which is a new compound can be obtained byisomerisation and simultaneous reduction of the epoxide XVI a ##STR36##according to a procedure analogous to that followed for converting XVIinto V γ-a [see above, cf. Tetrahedron 19, 1091 (1963) and J. Org. Chem.26, 3615 (1961)].

According to another method of the invention, compounds of formula XIIare prepared by cyclising by means of an acidic or basic agent compoundshaving the formula ##STR37## containing one double bond in position 2'-or 3'- of the acyl side-chain, the double bond being represented by adotted line, and wherein the symbols R have the same meaning as informula XII and the index n is zero or 1.

The above cyclisation can be carried out by using the same type ofacidic or basic reagents as those mentioned for converting compounds XIto their corresponding bicyclic derivatives X i. Preferably, there isused, as cyclising agent, BF₃ in an inert organic solvent such as, forexample, benzene, toluene or ether, or a mixture thereof.

The present invention describes also a method for the preparation ofcyclic ketones of formula XIV which comprises cyclising by means of heatcompounds of formula ##STR38## wherein the symbols R have the samemeaning as in formula XIV.

The reaction can be carried out in inert organic solvents such as, forexample, those already mentioned for the cyclisation of compounds XI orXIII. The temperature to which said cyclisation can occur is notcritical. It is preferable to operate at a temperature comprised between100° and 160°. At lower temperatures the reaction time can beconsiderably longer. At temperatures higher than those indicated thereaction time can be shorter; however, at these temperaturesfragmentation reactions can occur.

Specific examples of compounds comprises by the various structuralformulae shown hereinbefore include

2,4,6,6-tetramethyl-1-trans-crotonoyl-1-cyclohexene,

2,4,6,6-tetramethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene,

2,4,6,6-tetramethyl-1-trans-crotonoyl-1,3-cyclohexadiene,

2,5,6,6-tetramethyl-1-trans-crotonoyl-1-cyclohexene,

2,5,6,6-tetramethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene,

2,5,6,6-tetramethyl-1-trans-crotonoyl-1,3-cyclohexadiene,

2,5,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-1-cyclohexene,

2,6,6-trimethyl-1-[1-hydroxy-3-methyl-2-butenyl]-1-cyclohexene,

2,6,6-trimethyl-1-[3-methyl-2-butenoyl]-1-cyclohexene,

2,6,6-trimethyl-1-[3-methyl-2-butenoyl]-1,3-cyclohexadiene,

2,3,6,6-tetramethyl-1-crotonoyl-2-cyclohexene,

2,3,6,6-tetramethyl-1-[1-hydroxy-2-butenyl]-2-cyclohexene,

2,6,6-trimethyl-1-vinylacetyl-1-cyclohexene,

2,6,6-trimethyl-1-[3-methyl-3-butenoyl]-1-cyclohexene,

2,6,6-trimethyl-1-[2-pentenoyl]-2-cyclohexene,

7,11-dimethyl-5-oxo-3,6,10-dodecatriene,

2,6,6-trimethyl-1-[2-methylcrotonoyl]-2-cyclohexene,

2,6,6-trimethyl-1-[3-methylcrotonoyl]-2-cyclohexene,

2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane,

2,6,6-trimethyl-1-vinylacetyl-1,2-epoxycyclohexane,

2,6,6-trimethyl-1-[1-hydroxy-3-butenyl]-1-cyclohexene,

2,6,6-trimethyl-1-[1-hydroxy-3-butenyl]-1,2-epoxycyclohexane,

2,6,6-trimethyl-1[1-hydroxy-2-butenyl]-1,2-epoxycyclohexane,

2,6,6-trimethyl-1-[1-hydroxy-3-butenyl]-2-cyclohexane,

2,6,6-trimethyl-1-vinylacetate-2-cyclohexane,

2,6,6-trimethyl-1-hydroxy-1-crotonoyl-2-cyclohexene,

1,5,5,8,9-pentamethylbicyclo[4.3.0]non-8-en-7-one,

1,4,5,5,8,9-hexamethylbicyclo[4.3.0]non-8-en-7-one,

4,4,8-trimethyl-9-methylene-bicyclo[3.3.1]nonan-6-one,

1,5,5,9-trimethylbicyclo[4.3.0]nona-2,8-dien-7-one,

1,5,5,9-tetramethylbicyclo[4.3.0]non-8-en-7-ol,

1,5,5,9-tetramethylbicyclo[4.3.0]non-8-en-7-one,

6,6-dimethyl-2-methylene-1-crotonoylcyclohexane,

2,6,6-trimethyl-1-[1-hydroxy-2-butynyl]-1-cyclohexene,

2,6,6-trimethyl-1-[1-hydroxy-2-butynyl]-2-cyclohexene,

cis- and trans-2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene,

2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-2-cyclohexene,

6,10-dimethyl-4-oxo-2,5,9-undecatriene,

cis- and trans-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene,

cis- and trans-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene,

trans-2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene,

2,6,6-trimethyl-1-tetrolyl-1-cyclohexene and

2,6,6-trimethyl-1-tetrolyl-2-cyclohexene.

cis- andtrans-2,3,6,6-tetramethyl-1-[2-methyl-2-butenoyl]-1,3-cyclohexadiene,

2,3,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-1,3-cyclohexadiene

cis- and trans-2,3,6,6-tetramethyl-1-[2-pentenoyl]-1,3-cyclohexadiene,

cis- and trans-2,3,6,6-tetramethyl-1-crotonoyl-1,3-cyclohexadiene,

cis- andtrans-2,4,6,6-tetramethyl-1-[2-methyl-2-butenoyl]-1,3-cyclohexadiene,

2,4,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-1,3-cyclohexadiene

cis-2,4,6,6-tetramethyl-1-crotonoyl-1,3-cyclohexadiene,

cis- and trans-2,4,6,6-tetramethyl-1-[2-pentenoyl]-1,3-cyclohexadiene,

cis- andtrans-2,5,6,6-tetramethyl-1-[2-methyl-2-butenoyl]-1,3-cyclohexadiene

2,5,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-1,3-cyclohexadiene,

cis- and trans-2,5,6,6-tetramethyl-1-[2-pentenoyl]-1,3-cyclohexadiene,

cis-2,5,6,6-tetramethyl-1-crotonoyl-1,3-cyclohexadiene,

cis- andtrans-2,6-dimethyl-6-ethyl-1-[2-methyl-2-butenoyl]-1,3-cyclohexadiene,

2,6-dimethyl-6-ethyl-1-[3-methyl-2-butenoyl]-1,3-cyclohexadiene

cis- and trans-2,6-dimethyl-6-ethyl-1-[2-pentenoyl]-1,3-cyclohexadiene,

cis- and trans-2,6-dimethyl-6-ethyl-1-crotonoyl-1,3-cyclohexadiene

cis- andtrans-2,6,6-trimethyl-1-[2-methyl-2-butenoyl]-1,3-cyclohexadiene,

cis- and trans-2,6,6-trimethyl-1-[2-pentenoyl]-1,3-cyclohexadiene,

cis- andtrans-2,3,6,6-tetramethyl-1-[2-methyl-2-butenoyl]-2-cyclohexene,

2,3,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-2-cyclohexene,

cis- and trans-2,3,6,6-tetramethyl-1-[2-pentenoyl]-2-cyclohexene,

cis- andtrans-2,4,6,6-tetramethyl-1-[2-methyl-2-butenoyl]-2-cyclohexene,

2,4,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-2-cyclohexene,

cis- and trans-2,4,6,6-tetramethyl-1-[2-pentenoyl]-2-cyclohexene

cis- and trans-2,4,6,6-tetramethyl-1-crotonoyl-2-cyclohexene,

cis- andtrans-2,5,6,6-tetramethyl-1-[2-methyl-2-butenoyl]-2-cyclohexene,

2,5,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-2-cyclohexene,

cis- and trans-2,5,6,6-tetramethyl-1-[2-pentenoyl]-2-cyclohexene,

cis- and trans-2,5,6,6-tetramethyl-1-crotonoyl-2-cyclohexene,

cis- andtrans-2,6-dimethyl-6-ethyl-1-[2-methyl-2-butenoyl]-2-cyclohexene,

2,6-dimethyl-6-ethyl-1-[3-methyl-2-butenoyl]-2-cyclohexene,

cis- and trans-2,6-dimethyl-6-ethyl-1-[2-pentenoyl]-2-cyclohexene,

cis- and trans-2,6-dimethyl-6-ethyl-1-crotonoyl-2-cyclohexene,

cis- andtrans-2,3,6,6-tetramethyl-1-[2-methyl-2-butenoyl]-1-cyclohexene,

2,3,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-1-cyclohexene,

cis- and trans-2,3,6,6-tetramethyl-1-[2-pentenoyl]-1-cyclohexene

cis- and trans-2,3,6,6-tetramethyl-1-crotonoyl-1-cyclohexene,

cis- andtrans-2,4,6,6-tetramethyl-1-[2-methyl-2-butenoyl]-1-cyclohexene,

2,4,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-1-cyclohexene,

cis- and trans-2,4,6,6-tetramethyl-1-[2-pentenoyl]-1-cyclohexene,

cis- andtrans-2,5,6,6-tetramethyl-1-[2-methyl-2-butenoyl]-1-cyclohexene,

cis- and trans-2,5,6,6-tetramethyl-1-[2-pentenoyl]-1-cyclohexene

cis-2,5,6,6-tetramethyl-1-crotonoyl-1-cyclohexene,

cis- andtrans-2,6-dimethyl-6-ethyl-1-[2-methyl-2-butenoyl]-1-cyclohexene,

2,6-dimethyl-6-ethyl-1-[3-methyl-2-butenoyl]-1-cyclohexene,

cis- and trans-2,6-dimethyl-6-ethyl-1-[2-pentenoyl]-1-cyclohexene,

cis- and trans-2,6,6-trimethyl-1-[2-methyl-2-butenoyl]-1-cyclohexene,

cis- and trans-2,6,6-trimethyl-1-[2-pentenoyl]-1-cyclohexene,

cis- andtrans-3,6,6-trimethyl-2-methylene-1-[3-methyl-2-butenoyl]-cyclohexane,

cis- and trans-3,6,6-trimethyl-2-methylene-1-[2-pentenoyl]-cyclohexane,

cis- and trans-3,6,6-trimethyl-2-methylene-1-crotonoylcyclohexane,

cis- andtrans-4,6,6-trimethyl-2-methylene-1-[2-methyl-2-butenoyl]-cyclohexane,

4,6,6-trimethyl-2-methylene-1-[3-methyl-2-butenoyl]-cyclohexane,

cis- and trans-4,6,6-trimethyl-2-methylene-1-[2-pentenoyl]-cyclohexane,

cis- and trans-4,6,6-trimethyl-2-methylene-1-crotonoylcyclohexane,

cis- andtrans-5,6,6-trimethyl-2-methylene-1-[2-methyl-2-butenoyl]-cyclohexane,

5,6,6-trimethyl-2-methylene-1-[3-methyl-2-butenoyl]-cyclohexane,

cis- and trans-5,6,6-trimethyl-2-methylene-1-[2-pentenoyl]-cyclohexane,

cis- and trans-5,6,6-trimethyl-2-methylene-1-crotonoylcyclohexane,

cis- andtrans-6-ethyl-6-methyl-2-methylene-1-[2-methyl-2-butenoyl]-cyclohexane,

6-methyl-6-methyl-2-methylene-1-[3-methyl-2-butenoyl]-cyclohexane,

cis- and trans-6-ethyl-6-methyl-2-methylene-1-[2-pentenoyl]-cyclohexane,

cis- and trans-6-ethyl-6-methyl-2-methylene-1-crotonoylcyclohexane,

cis- andtrans-6,6-dimethyl-2-methylene-1-[2-methyl-2-butenoyl]-cyclohexane,

6,6-dimethyl-2-methylene-1-[3-methyl-2-butenoyl]-cyclohexane,

cis- and trans-6,6-dimethyl-2-methylene-1-[2-pentenoyl]-cyclohexane,

2,6,6-trimethyl-1-[3-methyl-3-butenoyl]-2-cyclohexene and

cis- and trans-2,6-dimethyl-6-ethyl-1-crotonoyl-1-cyclohexene.

The invention will be illustrated in a more detailed manner by thefollowing Examples. In said Examples temperatures are given in degreescentigrade.

EXAMPLE 1 2,4,6,6-Tetramethyl-1-trans-crotonoyl-1-cyclohexene

A mixture of 10 g. of2,4,6,6-tetramethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene, preparedaccording to paragraphe (f) hereinafter, 100 g. of activated MnO₂ and3CO ml. of pentane was stirred at 20° in an atmosphere of argon during45 h. After filtration the solid was washed with pentane and the clearfiltrate was brought to dryness. The residue obtained from the aboveoperation was dissolved in 100 ml. of dry benzene, added of 160 mg. ofp-toluensulfonic acid and allowed to react at room temperature in argonatmosphere during 16 h. By extracting with ether in the presence ofNaHCO₃ (5 % solution) and collecting the organc layers, 7.96 g. (80 %)of 2,4,6,6-tetramethyl-1-trans-crotonoyl-1-cyclohexene were obtainedafter distillation in vacuo. B.p. 60°-2°/0.001 Torr. Purification bycolumn chromatography (H₂ SiO₃ benzene) gave a pure sample; theanalytical data were as follows: d₄ ²⁰ =0.9223; n_(D) ²⁰ =1.4919; I.R.:ν=970 (--CH═CH--trans), 1615, 1645, 1670 cm⁻¹ (C═C, C═O); Mass spectrum:M⁺ = 206; NMR.: 0.80- 1.05 (6 H, m, 2 CH₃ --), 1.09 (3 H, s, ##STR39##1.48 (3 H, s, ##STR40## 1.88 (3 H, d.d., J= 6.5 and ca. 1 cps,--CH═CH--CH₃), 1.2-2.2 (5 H, m), 6.00 (1 H, d. q., J= 16 and ca. 1 cps,--CH--CH═CH--CH₃), 6.63 (1 H, d. q., J= 16 and 6.5 cps,--CO--CH═CH--CH₃), UV.: λ_(max) = 225 mη (ε^(EtOH) = 12,390)

C₁₄ H₂₂ O Cal.ed: C 81.50; H 10.75 %. Found: C 81.49; H 10.89.

2,4,6,6-Tetramethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene used asstarting material in the above preparation can be obtained as follows:

(a) 4-Methyl-3-penten-2-ol

according to Helv. Chim. Acta 30, 2216 (1947).

Mesityl oxide (245 g.) dissolved in 1200 ml of dry ether was added atreflux temperature to a mixture of LiAlH₄ (30 g.) in 200 ml. of the samesolvent (1 h.). The mixture was allowed to react at 20° during 2 h. andafter decomposition of the excess of LiAlH₄ by means of wet ether, itwas added to a solution of 200 g. of NH₄ Cl in 1 l. of water.

After extraction with ether, the usual treatments gave 221 g. (88%) of4-methyl-3-penten-2-ol; B.p. 47°-50°/11 Torr. The product thus obtainedwas wet and it was conveniently dried by treatment with anhydrous K₂ CO₃in pet.-ether (30°-50°).

d₄ ²⁰ =0.8421; n_(D) ²⁰ =1.4388;

IR.: ν=1050 (C--O), 1670 (C═C), 3350 cm⁻¹ (OH)

MS.: M⁺ =100

NMR.: 1.11 (3 H, d, J=6 cps), 1.64 (6 H, m), 4.04 (1 H, s), 4.15-4.65 (1H, m), 5.10 (1 H, d, J=Ca. 8 cps). δ ppm.

C₆ H₁₂ O Cal. ed: C 71.95; H 12.08%. Found: C 71.83; H 12,19.

(b) 4-Bromo-2-methyl-2-pentene

according to Helv. Chim. Acta 30, 2216 (1947).

4-Methyl-3-penten-2-ol (220 g) in 250 ml. of pet.-ether (30°-50°) anddry pyridine (41 g.) was added to a solution of freshly distilled PBr₃(233 g.) and 10 drops of dry pyridine at -20° (1 h.). The reactionmixture was directly distilled and 274 g. (76%) of4-bromo-2-methyl-2-pentene were obtained. Owing to its instability, theproduct must be employed without too long storage.

(c) 4,6-Dimethyl-5-heptene-2-one

according to Helv. Chim. Acta 30, 2216 (1947).

The bromide (274 g.), obtained according to paragraph (b) hereinabove,was added at a temperature comprised between -5 and -10° toacetylacetate (obtained from 40.7 g. of sodium and 230 g. of ethylacetylacetate) in 670 ml. of anhydrous ethanol. The reaction mixture wasallowed to react during 2 days at 20° and, after the usual treatments ofextraction and drying, 252 g. of the ketoester intermediate wereobtained. This substance was dissolved in 928 ml. of ethanol, added to asolution of Ba(OH)₂.8 H₂ O (444 g in 3280 ml. of water), and kept toreflux during 2 h.

The precipitate which was formed during the above operation wasdissolved with 10% HCl, extracted with ether and subjected to the usualtreatments.

142 g. (85%) of product having B.p. 53°-7°/10 Torr were obtained. 70% ofthis product was constituted by 4,6-dimethyl-5-hepten-2-one and 30% bythe allylic isomer.

The separation by means of preparative v.p.c. gave the two productswhich showed the following analytical data:

4,6-dimethyl-5-hepten-2-one

IR.: ν 830, 1360 (CH₃ CO), 1710 cm⁻¹ (CO)

MS.: M⁺ =140

NMR.: 0.89 (3 H, d, J=6.5 cps), 1.62 (6 H, s), 2.00 (3 H, s), 2.22 (2 H,d, J=7 cps.), 2.5-3.2 (1 H, m), 4.83 (1 H, d, J=8 cps) δ ppm.

4,4-dimethyl-5-hepten-2-one

MS.: M⁺ =140

NMR.: 1.07 (6 H, s), 1.63 (3 H, d, J=4.5 cps), 1.99 (3 H, s), 2.28 (2 H,s), 5.40 (2 H, m) δ ppm.

The mixture of these two isomers can be used as such in the followingstep. It must be noted that the rearranged structure will be eliminatedduring the successive cyclisation reaction (see paragraph e).

(d) 2,4,6-Trimethyl-2,6-octadienal

according to Tetrahedron Suppl. No. 8, Part I, 347 (1966).

Diisopropylamino (44.8 g.) in 100 ml. dry ether was added in anatmosphere of argon to a solution of butyllithium (14% in hexane) in 200ml. of dry ether and the mixture was then allowed to react at 20° during2 h.

55 g. of ethylidencyclohexylamine were then added to the above mixtureat 0°, followed by the addition at -70° of 70 g. of the ketones obtainedaccording to paragraph (c) above. The reaction mixture was left at -70°during 11/2 h., then at 20° during one night. After addition of 800 ml.of 20% acetic acid at 0°, stirring during 3 h. at 20° in an atmosphereof argon and extraction followed by the usual treatments, threefractions were obtained.

Fraction I: B.p. 30°-52°/0.01 Torr; 4.6 g.

Fraction II: B.p. 52°-70°/0.5 Torr; 44.6 g. (53%)

Fraction III: B.p. 70°-80°/0.01 Torr; 5.1 g.

Residue 17 g.

Fraction II was redistilled and analysed by NMR. It was constituted by amixture (ca. 3:2) of two isomeric aldehydes:2,4,6-trimethyl-2,6-octadienal and 4,4,6-trimethyl-2,6-octadienal. Thismixture was used for the next step.

(e) 4-Methyl-β-cyclocitral

A mixture of the two isomeric aldehydes obtained according to paragraph(d) (36.5 g.), aniline (21.4 g.) and anhydrous sodium sulphate (20 g.)in 55 ml. of ether was left at 20° under stirring during one night.After having filtered washed and concentrated to the initial volume thesolution was poured with vigorous stirring into 221 ml. of conc. H₂ SO₄and 22.1 g. of ice. The temperature was kept between -20 and -25° during1 h., and the mixture was then added to 300 g. of ice and immediatelydistilled by means of steam distillation. The distillate was saturatedwith NaCl, extracted with ether and treated as usual. 36 g. of a mixtureof crude α- and β-cyclocitral were thus obtained. The subsequentisomerisation was carried out at -10° in 120 ml. of a 8.5% Chanolic KOHsolution (80% ethanol). The mixture was allowed to react during 3 h. inan atmosphere of argon, diluted then with pet.-ether (30°-50°), pouredinto 400 ml. of a NaCl saturated aqueous solution and finally extractedwith pet.-ether. By distillation 4-methyl-β-cyclocitral was obtained:

Fraction I: B.p. 30°-73°/10 Torr; 1.4 g.

Fraction II: B.p. 90°-95°/10 Torr; 18.6 g. (51%)

Residue 6 g.

d₄ ²⁰ =0.9564; n_(D) ²⁰ =1.4847

IR: ν=1610, 1670, 1720 (C═C; C═O), 2760, 2820 cm⁻¹ (CHO)

MS: M⁺ =166

NMR: 0.92 (3 H, d, J=ca. 4 cps), 1.13 (6 H, s), 2.05 (3 H, s), 1.0-2.30(5 H, m), 10.22 (1 H, s) δ ppm.

UV: λ_(max) ^(EtOH) =248 mn (ε=9416)

C₁₁ H₁₈ O Cal.ed: C 79.46; H 10.92%. Found: C 79.39; H 10.86.

(f) 2,4,6,6-Tetramethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene

A solution of 16.4 g. of 4-methyl-β-cyclocitral obtained according toparagraph (c) in 20 ml. dry ether was added (35 min.) at -20° to asolution of propenyl lithium. This latter solution was freshly preparedby adding at -10° a solution of 9.7 g. of 1-chloropropene in 80 ml. ofdry ether to 1.85 g. of granulated lithium containing 1% of sodium.After being left 3 h. at 20° this lithium salt solution was ready forthe addition of citral as described above.

After complete addition, the reaction was allowed to react at -15°/-20°during 5 h., left at 20° during one night and poured then into 60 g. ofNH₄ Cl in water/ice. The reaction mixture was then extracted with etherand the ethereal combined extracts were concentrated at 40°-50° invacuo, the product is thermolabile.

Fraction I: B.p. 30°-55°/0.001 Torr, 0.5 g.

Fraction II: B.p. 55°-8°/0.001 Torr, 18.6 g. (90%)

Fraction II represents2,4,6,6-tetramethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene in a cis- andtrans- mixture.

d₄ ²⁰ =0.9300; n_(D) ²⁰ =1.4933

IR: ν=97.0 (--CH═CH-trans), 1030 (CO), 1645 (C═C), 3400 cm⁻¹ (OH)

MS: M⁺ =208

NMR: 0.8-1.2 (9 H, m), 1.5-1.8 (6 H, m), 1.0-2.3 (5 H, m), 2.4 (1 H, s,wide band), 4.65 (1 H, m), 5.55 (2 H, m) δ ppm.

C₁₄ H₂₄ O Cal.ed: C 80.71; H 11.61%. Found: C 80.71; H 11.48%.

EXAMPLE 2 2,4,6,6-Tetramethyl-1-trans-crotonoyl-1,3-cyclohexadiene

2,4,6,6-Tetramethyl-1-trans-crotonoyl-1-cyclohexene (4.86 g.) obtainedaccording to Example 1, was stirred at 50° with N-bromosuccinimide (5.85g.), bis-azo-isobutyronitrile (0.6 mg.), 40 ml. of CH₂ Cl₂ and 40 ml. ofCCl₄ in a moisture-free vessel. After 50 min. the solution became cleardue to the solution of NBS and succinimide precipitated. The mixture wasstirred 5 min. more at 50° then, after cooling at 20°, diethylamine(10.6 g.) was added to it with stirring. After addition of 100 ml. ofpet.-ether (30°-50°), homogenization and filtration, the filtrate gaveby evaporation (at 40° under vacuum) and subsequent heating at 135°-145°during one hour, 3.60 g. (75%) of a mixture 45:55 of the initial ketoneand the final product. These two compounds were separated by v.p.c.(Carbowax 15%, 200°, 2.5 m.).

2,4,6,6-Tetramethyl-trans-1-crotonoyl-1,3-cyclohexadiene can also beseparated by column chromatography (40 parts by weight SiO₂ in thepresence of benzene).

d₄ ²⁰ =0.9431, n_(D) ²⁰ =1.5115

IR: ν=970 (--CH═CH-trans), 1620-1670 cm⁻¹ (C═C, C═O)

MS: M⁺ =204

NMR: 1.00 (6 H, s), 1.60 (3 H, s), 1.89 (3 H, d.d., J=6.5 and ca. 1cps), 1.80 (3 H, s), ca. 1.7-1.9 (2 H, m), 5.52 (1 H, s wide), 6.05 (1H, d. q., J=16 and ca. 1 cps), 6.72 (1 H, d. q., J=16 and 6.5 cps.) δppm.

UV: λ_(max) ^(EtOH) =227 mη (β=15,090)

C₁₄ H₂₀ C Cal.ed: C 82.30; H 9.87%. Found: C 82.43; H 10.09.

EXAMPLE 3 2,5,6,6-Tetramethyl-1-trans-crotonoyl-1-cyclohexene

A mixture of 8.0 g. of2,5,6,6-tetramethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene, preparedaccording to paragraph (e) hereinafter, 80 g. of activated MnO₂ and 250ml of pentane was stirred at 20° in an atmosphere of argon during 21 h.After filtration the solid was thoroughly washed with pentane and theclear filtrate was brought to dryness. The residue thus obtained (8 g.),which was constituted by 81% of the desired ketone, 16% of itscis-isomer and 3% impurity (v.p.c. Carbowax 15%, 200°, 2.5 m.), wasdissolved in 80 ml. of dry benzene, added of 160 mg. of p-toluensulfonicacid and allowed to react at room temperature in an atmosphere of argonduring 16 h. By extracting with ether in the presence of NaHCO₃ (5%solution) and collecting the organic layers, 6.83 g. (86%) of2,5,6,6-tetramethyl-1-trans-crotonoyl-1-cyclohexene were obtained byvacuum distillation, B.p. 64°-7°/0.001 Torr.

d₄ ²⁰ = 0.9426; n_(D) ²⁰ = 1.5016

IR: ν = 970, 1615, 1640, 1670 cm⁻¹.

MS: M⁺ = 206

NMR: 0.8-1.0 (9 H, m); 1.47 (3 H, s); 1.87 (3 H, d.d., J= 6.5 and ca. 1cps); 6.58 (1 H, d.q., J= 16 and 6.5 cps) δ ppm.

UV: λ_(max) ^(EtOH) = 227 mη (ε = 11,545)

C₁₄ H₂₂ O Cal.ed: C 81.50; H 10.75%. Found: C 81.27; H 10.46%.

2,5,6,6-Tetramethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene used asstarting material in the above preparation can be obtained as follows:

(a) 1-Bromo-2,3-dimethyl-2-butene

according to Helv. Chim. Acta 23, 964 (1940).

Hydrobromic acid (600 g., 30% in acetic acid) was added under stirringto dimethylbutadiene (200 g.) at a temperature comprised between -25 and-15° during 1.5 h. After having been left 2 days at room temperature,the mixture was poured into ice-water and extracted with ether. Theorganic layer after the usual treatments gave two fractions:

Fraction I: B.p. 30°-40°/10 Torr, 60 g.

Fraction II: B.p. 42°-4°/10 Torr, 261 g. (72%) of the desired product.

Residue, 50 g.

(b) 5,6-Dimethyl-5-hepten-2-one

according to Helv. Chim. Acta 23, 964 (1940).

The bromide (261 g.), obtained according to paragraph (a) hereinabove,was added at 6°-10° to acetyl acetate (obtained from 38.8 g. of sodiumand 219 g. of ethylacetacetate) in 600 ml of anhydrous ethanol. Thereaction mixture was allowed to react during one night at 20° and atreflux during 1.5 h. After dilution with 5-fold its volume of water andthe usual treatments of extraction and drying, 263 g. (77%) of theketoester intermediate were obtained. The distillation gave also afraction with B.p. 30°-42°/0.001 Torr, 35 g., and a residue of 0.5 g.

The ketoester was dissolved in 960 ml. of ethanol, added to a solutionof Ba(OH)₂.8 H₂ O (460 g. in 3400 ml. of water) and kept boiling during22 h.

The precipitate which was formed during the above operation wasdissolved with 10% HCl, extracted with ether and subjected to the usualtreatments.

144 g. (83%) of a product having B.p. 70°-1°/10 Torr were obtained.Together with this product a fraction having B.p. 69°/10 Torr and aresidue of 3.0 g. were obtained.

5,6-Dimethyl-5-hepten-2-one shows the following analytical constants:

d₄ ²⁰ = 0.8661; n_(D) ²⁰ = 1.4500

IR: ν = 1350, 1710 cm⁻¹.

MS: M⁺ = 140

NMR: 1.63 (9 H, s); 2.07 (3 H, s); 2.30 (4 H, m) δ ppm.

C₉ H₁₆ O Calc.ed: C 77.09; H 11.50%. Found: C 77.11; H 11.69%.

(c) 3,6,7-Trimethyl-2,6-octadienal

according to Tetrahedron Suppl. No. 8, Part I, 347 (1966)

Methyl iodide (79.8 g.) in 250 ml. of dry ether was added at -15°, to asuspension of lithium (7.77 g) and 150 ml. of dry ether and the mixturewas then allowed to react at 20° during 24 h.

Diisopropylamine (55.7 g.) in 100 ml. dry ether was added to the abovemixture and left to react at 20° during 2 h.

68.7 g. of ethylidencyclohexylamine [see Bull. Soc. Chim. France 1947,715] were added, followed by the addition at -70° of 70 g. ofdimethylheptenone.

After the same treatment described in Example 1, paragraph d, 2fractions were obtained:

Fraction I: B.p. 30°-53°/0.001 Torr; 4.5 g.

Fraction II: B.p. 53°-65°-69°/0.001 Torr; 46.1 g. (55%)

Residue 28 g.

Fraction II is a mixture ca. 1:2 of cis- andtrans-3,6,7-trimethyl-2,6-octadienal which can be separated by v.p.c.(Carbowax, 15%, 200°, 2.5 m.).

The mixture showed the following data:

d₄ ²⁰ = 0.8912; n_(D) ²⁰ = 1.4919

IR: ν = 1630, 1660, 1715 (C═C, C═O), 1730, 2860 cm⁻¹ (CHO)

MS: M⁺ = 166

NMR: 1.62 (9 H, s), 1.8-2.7 (7 H, complex band), 5.67 (1 H, d, J= 7.5cps), 10.05 (1 H, almost t, J= 7.5 cps, die tp ,oxomg pf twp d) δ ppm.

C₁₁ H₁₈ O Cal.ed: C 79.46; H 10.92%. Found: C 79.21; H 10.80.

(d) 5-Methyl-β-cyclocitral

A mixture of the two isomeric aldehydes obtained according to paragraph(c) (38 g.), aniline (22.3 g.) and anhydrous sodium sulphate (20 g.) in23 ml. of ether was treated as described in Example 1, paragraph (c),using 230 ml. of conc. H₂ SO₄ and 23 g. of ice.

After steam distillation, saturation with NaCl and extraction 32 g.(84%) of a 2:3 mixture of 5-methyl-α- and 5 -methyl-β-cyclocitrals wereobtained. The subsequent isomerisation was carried out at -10° in 120ml. of a 8.5% ethanolic KOH solution (80% ethanol). By the treatmentdescribed in Example 2, (e) 27.6 g. (86%) of a product with B.p.48°-54°/0.001 Torr were obtained. This product consists of 3-4% of theα- and 96-7% of the β-isomer.

d₄ ²⁰ = 0.9528; n_(D) ²⁰ = 1.4990

IR: ν = 1610, 1670, 1710, 2760, 2860 cm⁻¹

MS: M⁺ = 166

NMR: 0.89 (3 H, m); 1.03 (3 H, s); 1.18 (3 H, s); 2.08 (3 H, s); 1.2-2.4(5 H, m); 10.27 (1 H, s) δ ppm.

UV: λ_(max) ^(EtOH) = 248 mη (ε = 10,546)

C₁₁ H₁₈ O Calc.ed: C 79.46; H 10.92%. Found: C 79.43; H 10.80%.

(e) 2,5,6,6-Tetramethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene

A solution of 16.6 g. of 5-methyl-β-cyclocitral obtained according toparagraph (d) hereabove in 20 ml. dry ether was added (35 min.) at -20°to a solution of propenyl lithium. This solution was freshly preparedaccording to Example 1, paragraph (f). The same treatment gave bydistillation three fractions:

Fraction I: B.p. 40°-56°/0.001 Torr, 1.5 g.

Fraction II: B.p. 57°-62°/0.001 Torr, 1.3 g.

Fraction III: B.p. 64°-7°/0.001 Torr, 9.9 g. (47.5%) of the desiredproduct.

d₄ ²⁰ = 0.9656; n_(D) ²⁰ = 1.5055

IR: ν = 970, 1670, 3400 cm⁻¹.

MS: M⁺ = 208

NMR: 0.8-0.9 (3 H, m); 0.95 (6 H, s); 1.0-2.2 (12 H, m); 4.80 (1 H, s);5.70 (2 H, m) δ ppm.

C₁₄ H₂₄ O calc.ed: C 80.71; H 11.61%. Found: C 80.83; H 11.54%.

EXAMPLE 4 2,5,6,6-Tetramethyl-1-trans-crotonoyl-1,3-cyclohexadiene

2,5,6,6-Tetramethyl-1-trans-crotonoyl-1-cyclohexene (4.86 g.), obtainedaccording to Example 3, was allowed to react, according to the sameprocedure described in Example 2 for the preparation of thecorresponding 2,4,6,6-tetramethyl derivative with N-bromosuccinimide(5.85 g.) bis-azo-isobutyronitrile (0.6 mg.), 40 ml. of CH₂ Cl₂ and 40ml. of CCl₄. By the usual treatment 3.71 g. (77%) of a product at B.p.75°/0.001 Torr were obtained.

d₄ ²⁰ = 0.9863; n_(D) ²⁰ = 1.5139

IR: ν = 970, 1610, 1630, 1670 cm⁻¹.

MS: M⁺ = 204

NMR: 0.89 (3 H, s); 1.02 (3 H, s); 0.97 (3 H, d, J = ca. 8 cps); 1.58 (3H, s); 1.88 (3 H, d. d., J= 6.5 and ca. 1 cps); 1.8-2.3 (1 H, m); 5.60(2 H, m); 6.0 (1 H, d.q., J= 16 and ca. 1 cps); 6.70 (1 H, d.q., J= 16and 6.5 cps) δ ppm.

UV: λ_(max) ^(EtOH) = 228 mη (ε = 11,640).

EXAMPLE 5 2,5,6,6-Tetramethyl-1-[3-methyl-2-butenoyl]-1-cyclohexene

5-methyl-β-cyclocitral (11.0 g.) [cf. Example 3, paragraph d)] in 30 ml.THF was added at -10° to a Grignard solution obtained from 2.4 g. ofmagnesium and 13.5 g. of 1-bromo-2-methyl-propene in 30 ml. of drytetrahydrofurane.

The reaction mixture was allowed to react during 2 h. at -5-0° andbrought then at room temperature during one night.

The usual treatment with NH₄ Cl at 0° and extraction gave:

Fraction I: B.p. 40°/0.001 Torr; 1.3 g.

Fraction II: B.P. 70°-2°/0.001 Torr; 8.7 g. (59%) of the desiredproduct.

Residue: 4 g.

IR: ν = 1020, 3400 cm⁻¹

MS: M⁺ = 222

NMR: 0.65-1.10 (9 H, m); 1.6-2.0 (9 H); 2.45 (1 H, s); 1.0-2.2 (5 H, m);4.9 (1 H; almost d, J= ca. 8 cps); 5.50 (1 H, almost d, J= ca. 8 cps) δppm.

The alcohol obtained above (6.4 g.) with MnO₂ (64 g.) in 190 ml. ofpentane was left at 20° during 42 h. in an atmosphere of argon. Theusual treatment [cf. Example 1] gave 5.3 g. of crude product. Two columnchromatography runs, on 40 parts by weight of H₂ SiO₃ and 24 parts byweight of H₂ SiO₃ respectively, enabled to obtain pure2,5,6,6-tetramethyl-1-[3-methyl-2-butenoyl]-1-cyclohexene.

B.p. 80°/0.001 Torr; d₄ ²⁰ = 0.9353; n_(D) ²⁰ = 1.5040

IR: ν = 1605, 1665 cm⁻¹

MS: M⁺ = 220

NMR: 0.80-1.10 (9 H, m); 1.53 (3 H, s); 2.14 (3 H, s); 1.39 (3 H,s);1.3-2.3 (5 H, m); 6.06 (1 H, s) δ ppm.

UV: λ_(max) ^(EtOH) =244 mη(ε=13,510)

C₁₅ H₂₄ O Calc.ed: C 81.76; H 10.98% Found: C 81.47; H 10.87.

EXAMPLE 6 2,6,6-Trimethyl-1-[1-hydroxy-3-methyl-2-butenyl]-1-cyclohexane

A solution of 1-chloro-2-methyl-propene (47.5 g.) in 50 ml. of dry etherwas added at -10° (1/2h) to a suspension of granulated lithium (7.6 g.,containing 1% of sodium, in 50 ml. of dry ether) in an argon atmosphere.

The reaction mixture was allowed to react at room temperature during 3h., then β-cyclocitral (63 g.) was added to it at -15°. After 5 morehours at that temperature the mixture was kept overnight at 20°, pouredinto a ice-cold aqueous solution of NH₄ Cl and finally extracted withether.

After evaporation of the ether in vacuo at a temperature below 40°-50°(the product is thermolabile), 76 g. of crude alcohol were obtained. Bycareful distillation in the presence of traces of Na₂ CO₃ two fractionswere obtained:

Fraction I: B. p. 47°-55°/0.001 Torr, 16.1 g.

Fraction II: B. p. 55°-60°/0.001 Torr, 21.4 g. (24.8%) of the desiredproduct.

Fraction II solidified by cooling and was recrystallised with pet.-ether(30°-50°) at -10°.

M.p. 55°-56.5°

MS: M⁺ =208

IR: 1020, 1650, 3400-3600 cm⁻¹.

NMR: 0.87 (3 H, s), 1.13 (3 H, s), 1.70-1.80 (9 H, m), 1.20-2.30 (6 H,m), 3.27 (1 H, s), 4.85 (1 H, d, J= 8 cps), 5.46 (1 H, almost d, J=8cps) δ ppm.

C₁₄ H₂₄ O Calc.ed: C 80.71; H 11.61% Found: C 80.65; H 11.54%.

EXAMPLE 7 2,6,6-Trimethyl-1-[3-methyl-2-butenoyl]-1-cyclohexene

2,6,6-Trimethyl-1-[1-hydroxy-3-methyl-2-butenyl]-1-cyclohexene, preparedaccording to Example 6, (1.0 g.) with activated MnO₂ (10 g.) in 30 ml.of pentane was mixed at room temperature during 63 h. after filtrationand distillation 630 mg. (63%) of the desired ketone, B.p. 67°/0.001Torr, were obtained.

d₄ ²⁰ =0.9310; n_(D) ²⁰ =1.5029

IR: ν=1605, 1665 cm⁻¹.

MS: M⁺ =206

NMR: 1.04 (6 H, s), 1.55 (3 H, s), 1.89 (3 H, d, J=ca. 1 cps), 2.15 (3H, s), 1.20-2.20 (6 H, m), 6.09 (1 H, s) δ ppm.

UV: λ_(max) ^(EtOH) =244 mη (ε=12,840).

C₁₄ H₂₂ O Calc.ed: C 81.50; H 10.75%. Found: C 81.27; H 10.77.

EXAMPLE 8 2,6,6-Trimethyl-1-[3-methyl-2-butenoyl]-1,3-cyclohexadiene

Under anhydrous conditions2,6,6-trimethyl-1-[3-methyl-2-butenoyl]-1-cyclohexene (2.1 g.) washeated to 45°-50° in the presence of N-bromosuccinimide (2.18 g.) in20.4 ml. of CH₂ Cl₂ and 20.4 ml. of CC1₄. The reaction mixture wasallowed to react until complete precipitation of succinimide (1 h.).

Diethylamine (3.46 ml.) was added to the above mixture at 20° followedby 51 ml. of pet.-ether (30°-50°). After filtration and evaporation (40°) of the clear filtrate, the residual product was heated at 130°-150° inan atmosphere of argon during 1 h., and, after cooling, poured into, anexcess of 10% HCl in the presence of pet.-ether and finally extractedwith more pet.-ether.

1.38 g. (66%) of a product with B.p. 70°/0.001 Torr were obtained. Thisfraction was constituted by a 1:1 mixture of starting material and finalproduct. Column chromatography (silicic ac. in the presence of benzene)gave a pure product:

d₄ ²⁰ =0.9566; n_(D) ²⁰ =1.5169

IR: ν=1602, 1660 cm⁻¹.

MS: M⁺ =204

NMR: 1.03 (6 H, s), 1.67 (3 H, s), 1.85 (3 H; d, J=ca. 1 cps), 2.02 (2H, s), 6.01 (1 H, s), δ ppm.

UV: λ_(max) ^(EtOH) =246 mn (ε=12,490); 309 mη (ε=2980).

C₁₄ H₂₀ O Calc.ed: C 82.30; H 9.87%. Found: C 82.15; H 10.12.

EXAMPLE 9 2,3,6,6-Tetramethyl-1-crotonoyl-2-cyclohexene

2,3,6,6-Tetramethyl-1-[1-hydroxy-2-butenyl]-2-cyclohexene (8.4 g.),obtained according to paragraph (e) of this Example, was oxidised andisomerised according to the same procedure described in Example 1.

The product obtained after purification by means of columnchromatography (silicic acid, benzene) was constituted by 1.31 g. (15.7%) of the desired ketone.

d₄ ²⁰ =0.9330; n_(D) ²⁰ =1.4976

IR: ν=970, 1620-1680 cm⁻¹.

MS: M⁺ =206

NMR: 0.80 (3 H, s), 0.90 (3 H, s), 1.50 (3 H, s), 1.55-2.40 (10 H,complex band), 2.82 (1 H, s), 6.19 (1 H, d.q., J=16 and ca.1 cps), 6.80(1 H, d.q., J=16 and 6.5 cps), δ ppm.

UV: λ_(max) ^(EtOH) =227 mη (ε=10,810)

C₁₄ H₂₂ O Calc.ed: C 81.50; H 10.75%. Found: C 81.81; H 11.00.

The carbinol used as starting material in the above preparation can beprepared as follows:

(a) 1-Bromo-3-methyl-butene

according to Helv. Chim. Acta 5, 750 (1922)

A 30% solution of hydrobromic acid (815 g.) in acetic acid were added(1.5 h.) at -20° to 200 g. of isoprene and the resulting mixture waskept 3 days at 0°, poured into 4 l. of cold water, decanted, dried overCaCl₂ and distilled to give the desired bromide. B.p. 24°-8°/10 Torr,312 g. (71%).

(b) 3,6-Dimethyl-5-hepten-2-one

according to Helv. Chim. Acta 30, 2213 (1947).

According to a procedure analogous to that described in paragraph c) ofExample 1, the bromide obtained above (312 g.) was added at atemperature comprised between -5 and -10° to acetylacetate (obtainedfrom 38.5 g. of sodium and 250 g. of ethyl α-methyl acetylacetate) in940 ml. of ethanol. The reaction mixture was allowed to react during 2days at 20° and, after the usual treatments of extraction and drying(cf. Example 1, paragraph (c) two fractions were obtained:

Fraction I: B.p. 41°-65°/0.001 Torr, 168 g.

Fraction II: B.p. 65°-70°/0.001 Torr, 219 g. (61%) of the ketoesterintermediate.

Residue: 17 g.

160 g. of the product of fraction II were brought to the boil withBa(OH)₂. 8 H₂ O (307 g.) in 2130 ml. of water and 665 ml. of ethanolduring 22 h. After the same treatment as in paragraph (c) of Example 1,two fractions were obtained:

Fraction I: B.p. 30°-55°/8 Torr, 2.3 g.

Fraction II: B.p. 55°-8°/8 Torr, 79.6 g. (75%) of the desired3,6-dimethyl-5-hepten-2-one:

d₄ ²⁰ =0.8495; n_(D) ²⁰ =1.4414

IR: ν=1350, 1710 cm⁻¹.

MS: M⁺ =140

NMR: 1.00 (3 H, d, J= 6.5 cps); 1.58 (3 H, s); 1.66 (3 H, s); 2.03 (3 H,s); 1.7-2.7 (3 H, m); 5.00 (1 H, t, J=7 cps) δ ppm.

C₉ H₁₆ O Calc.ed C 77.09; H 11.50%. Found C 76.81; H 11.40.

(c) 3,4,7-Trimethyl-2,6-octadienal

according to Tetrahedron Suppl. No. 8, Part 1, 347 (1966).

Diisopropylamine (56.1 g.) in 100 ml. dry ether were added under argonto a solution of butyl-lithium (275 g. of a 14% solution in hexane) in200 ml. of dry ether and the mixture was then allowed to react at 20°during 2 h..

68.7 g. of ethylidencyclohexylamine were added to 70 g. of the ketoneobtained according to paragraph (b) of this Example [cf. Example 1,paragraph d)].

The distillation gave:

Fraction I: B.p. 30°-52°/0.001 Torr, 0.8 g.

Fraction II: B.p. 52°-62°/0.001 Torr, 57 g. (68%) of the desiredproduct.

Residue: 22 g.

d₄ ²⁰ =0.8883; n_(D) ²⁰ =1.4866

IR: ν=1620, 1670, 1710 cm⁻¹.

MS: M⁺ =166

NMR: 1.06 (3 H, d, J=6 cps); 1.57 (3 H, s); 1.65 (3 H, s); 2.08 (3 H,s); 1.8-2.5 (3 H, m); 4.95 (1 H, t, J=ca. 7 cps); 5.68 (1 H, d, J=7.5cps); 9.79 (1 H, d, J=7.5 cps) δ ppm.

UV: λ_(max) ^(EtOH) =241 mη (ε=14,250).

C₁₁ H₁₈ O Calc.ed C 79.46; H 10.92%. Found: C 78.41; H 10.89.

(d) 3-Methyl-α-cyclocitral

The usual cyclisation procedure (cf. Example 1, paragraph (e)) gave 36g. of 3-methyl-α-cyclocitral from 46.6 g. of3,4,7-trimethyl-2,6-octadienal. The obtained α-cyclocitral contained 12%of the β-isomer:

Fraction I: B.p. 70°-8°/8 Torr, 4 g.

Fraction II: B.p. 81°-3.5°/8 Torr, 20.6 g.

Fraction III: B.p. 84°/8 Torr, 1.4 g.

Residue: 7 g.

Fraction II (yield 44%) contains 91% of 3-methyl-α-cyclocitral, 7% ofthe corresponding β-isomer and 2% of unknown impurity.

d₄ ²⁰ =0.9256; n_(D) ²⁰ =1.4805

IR: ν=1670, 1710, 2710, 2860 cm⁻¹.

MS: M⁺ =166

NMR: 0.87 (3 H, s); 0.95 (3 H, s); 1.52 (3 H, s); 1.68 (3 H, s); 1.0-2.4(5 H, m); 9.28 (1 H, d, J=5 cps) δ ppm.

λ_(max) ^(EtOH) =238 mη (ε=2850).

C₁₁ H₁₈ O Calc.ed: C 79.46; H 10.92%. Found: C 79.41; H 10.91.

(e) 2,3,6,6-Tetramethyl-1-[1-hydroxy-2-butenyl]-2-cyclohexane

3-Methyl-α-cyclocitral (20.5 g.) lithium (2.29 g.) and 1-chloropropene(11.9 g.) were allowed to react in 125 ml. of dry ether according to thesame procedure described in paragraph (f) of Example 1.

The distillation gave:

Fraction I: B.p. 30°-50°/0.001 Torr; 1.0 g.

Fraction II: B.p. 56°-9°/0.001 Torr; 16.8 g. (65%) of the desiredcarbinol.

Residue: 4 g.

The product of fraction II was used directly for the preparation of thecorresponding ketone.

EXAMPLE 10 2,6,6-Trimethyl-1-crotonoyl-1-cyclohexene

2,6,6-Trimethyl-1-vinylacetyl-1-cyclohexene (10 g.) was heated at 80°during 30 minutes with p-toluensulfonic acid (0.2 g.) and benzene (100ml.). After cooling, the solution was neutralised with a concentratedaqueous solution of Na₂ CO₃, washed with water, dried and distilledaccording to the usual procedure.Trans-2,6,6,-trimethyl-1-crotonoyl-1-cyclohexene, B.p. 84°-5°/0.001Torr; d₄ ²⁰ =0.9374; n_(D).sup. 20 =1.4989.

2,6,6-Trimethyl-1-vinylacetyl-1-cyclohexene, used as starting materialin the above preparation, was prepared as described in Example 11.

EXAMPLE 11 2,6,6-Trimethyl-1-vinylacetyl-1-cyclohexene and2,6,6-trimethyl-1-[3-methyl-3-butenoyl]-1-cyclohexene (cf. J. Am. Chem.Soc., 75, 422 (1953)).

At 0° and with vigorous stirring pure chromic anhydride (41 g.) wasadded portion-wise to 450 ml. of dry pyridine. To this solution2,6,6-trimethyl-1-[1-hydroxy-3-butenyl]-1-cyclohexene (44.5 g.) in 80ml. pyridine was then added dropwise at 0°. The reaction mixture waskept at this temperature during 30 minutes and allowed then to stand at20° for 10 hours.

The solution was poured into 1 l. of water and extracted with ether. Thecombined extracts were washed with a 10% aqueous HCl solution,neutralised with a 5% aqueous solution of Na₂ CO₃ and finally washedwith water. After the usual treatments followed by distillation,2,6,6-trimethyl-1-vinylacetyl-1-cyclohexene (60% yield) was obtained.n_(D) ²⁰ =1.4897; d₄ ²⁰ =0.9361.

By replacing hereabove2,6,6-trimethyl-1-[1-hydroxy-3-butenyl]-1-cyclohexene with2,6,6-trimethyl-1-[1-hydroxy-3-methyl-3-butenyl]-1-cyclohexene (n_(D) ²⁰=1.4939; d₄ ²⁰ =0.9270)2,6,6-trimethyl-1-[3-methyl-3-butenoyl]-1-cyclohexene was obtained;n_(D) ²⁰ =1.4862; d₄ ²⁰ =0.9307.

The hydroxylic compounds used as starting material in the abovedescribed preparation, have been prepared according to the usualconditions by a Grignard reaction between β-cyclocitral and allylbromide or between β-cyclocitral and methallyl chloride.

In a typical experiment 10.7 g. of Mg turnings and 5 g. of allyl bromidewere allowed to react in 70 ml. of dry ether. The reaction wasexothermic and the temperature of the reaction mixture increased up tothe boiling point of the solvent. To this solution allyl bromide (46 g.)and β-cyclocitral (61 g.) in 160 ml. of ether were added with vigorousstirring at such a rate as to maintain the ether at the boilingtemperature. The reaction mixture was then kept at reflux during 6 hoursand after cooling it was poured into a ice-cold concentrated aqueoussolution of NH₄ Cl. The ethereal layer after the usual treatments gave2,6,6-trimethyl-1-[1-hydroxy-3-butenyl]-1-cyclohexene (44.5 g.; 57%yield): B.p. 60°-2°/0.001 Torr; n_(D) ²⁰ =1.4964; d₄ ²⁰ =0.9398.

NMR spectrum (CCl₄): 0.98 (3 H, s); 1.10 (3 H, s); 1.82 (3 H, s);1.20-2.80 (9 H, m); 4.22 (1 H, m); 5.04 (2 H, d, J=15 cps); 5.88 (1 H,m) δ ppm.

By replacing in the above described preparation, allyl bromide with anequivalent of methallyl chloride, the corresponding carbinol wasobtained with similar yields.

EXAMPLE 12 Trans-2,6,6-trimethyl-1-crotonoyl-cyclohexene

17.6 g. of activated magnesium chips were suspended in 210 ml. ofabsolute tetrahydrofuran under nitrogen. Then a solution of 87.4 g. of1-bromopropene in 50 ml. of absolute tetrahydrofuran was added dropwiseat such a rate that the temperature was maintained between 40° and 45°.

When the addition of the bromine derivative was completed, the mixturewas refluxed for 45 minutes; then cooled to -10°, at which temperature110 g. of β-cyclocitral dissolved in 410 ml. of tetrahydrofuran wereintroduced dropwise within 45 minutes. Stirring was continued for 1 hourat -5°, then overnight at room temperature under nitrogen. The reactionmixture was poured into a suspension of 0.5 kg. of crushed ice in 1.5 l.of a saturated ammonium chloride solution. It was extracted 3 times withether, the extracts were combined and washed 3 times with water and thenwith a concentrated NaCl solution. After drying over anhydrous Na₂ SO₄the volatile portions were evaporated and the residue distilled. Therewere thus obtained 91 g. (65.2%) ofcis-2,6,6-trimethyl-1-[1-hydroxy-2-butonyl]-1-cyclohexene. B.p.64°-68°/0.01 Torr. By replacing in the above procedure the β-cyclocitralby its analogue α,cis-2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]2-cyclohexene was obtained.1700 ml. of absolute pyridine were cooled to 0°-5° and 154 g. of CrO₃were added portionwise within 30 minutes while stirring vigorously.Stirring was continued for 10 minutes at 5° and then 95 g. ofcis-2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene dissolved in300 ml. of pyridine were added dropwise within 20 minutes, whilemaintaining the temperature below 10°. When the addition was completedstirring was continued for 20 minutes, then the mixture was allowed tostand for 15 hours at room temperature. The reaction mixture was dilutedwith 5 l. of water and extracted with 6 portions of 800 ml. of ethereach. The extracts were combined and successively washed with: 4portions of water, 8 portions of 10% HCl at 0°, 3 portions of water, 2portions of 5% Na₂ CO₃, 2 portions of water. Moreover, each washingportion was extracted with ether before being discarded, and the extractwas added to the main extract after washing. The ethereal solution wasdried over anhydrous Na₂ SO₄, concentrated in vacuo and the residuedistilled. There were thus obtained 57 g. of a liquid fraction, b.p.75°-85°/0.001 Torr, which fraction was redistilled by means of aspinning band column and yielded 24 g. (25.5%) of puretrans-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene.

Analysis: Calc. for C₁₃ H₂₀ O: C 81.2% H 10.48%. Found: C 81.06 H 10.42.

d₄ ²⁰ =0.9378 n_(D) ²⁰ =1.4989

IR spectrum: 1675, 1640, 1618, 972 cm⁻¹

NMR spectrum: δ=0.98 ppm, (6 H, s); 1.48 ppm (3 H, s); 1.89 ppm, (3 H, dof d, J=6.5 cps and 1.2 cps); 1.2-2.1 ppm, (6 H, complex band); 6.0 ppm,(1 H, d of q, J=15 cps and 6.5 cps).

Mass spectrum: m/e=177, 69, 123, 192.

By replacing in the above procedurecis-2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene bycis-2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-2-cyclohexene,trans-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene was obtained which hadthe following characteristics: NMR spectrum: δ=0.83 ppm (3 H, s); 0.92ppm, (3 H, s); 1.55 ppm, (3 H, s broad); 1.89 ppm, (d of d, J=6.5 and1.1 cps); 1.0-2.3 ppm (4 H, complex band); 2.77 ppm, (1 H, s broad);5.52 ppm, (1 H, s broad); 6.18 ppm, (1 H, d of q, J=16 cps and 1.1 cps);6.77 ppm, (1 H, d of q, J=16 cps and 6.5 cps).

EXAMPLE 13 Cis-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene

To 80 ml. of pentane were added 15 g. of active MnO₂ and 1.6 g. of2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene prepared accordingto Example 12. The mixture was stirred for 5 days at room temperatureand then filtered. The precipitate was rinsed several times with pentaneand the rinsing fractions were added to the mother liquor. Afterconcentration in vacuo, the residue was distilled to obtain 1.1 g.(68.6%) of cis-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene, b.p.82°-85°0.001 Torr. The analysis of the product yielded similar resultsas those obtained for Example 12. The constants were the following: IRspectrum: 1665, 1640, 1605 cm⁻¹. Mass spectrum: m/e 177, 192, 123, 69.NMR spectrum: δ=1.03 ppm, (6 H, s); 1.55 ppm, (3 H, s); 2.1 ppm, (3 H,d, J=5.5 cps); 1.2-2.1 ppm, (6 H, complex band); 6.08 ppm, (2 H, complexband).

By replacing above 2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexeneby 2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-2-cyclohexene,cis-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene was obtained.

EXAMPLE 14 Trans-2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene

The following mixture was stirred for 24 hours at room temperature: 1 g.of trans-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene, 0.55 g. of NaHCO₃,0.44 g. of CaO and 1.17 g. of N-bromosuccinimide in 7 ml. of CC1₄.

1.7 ml. of diethylaniline was added, the mixture was diluted with 2volumes of petroleum ether (b.p. 30°-50°), filtered and the volatileportions were eliminated in vacuo (temperature <50°). Then it was heatedfor 2 hours on the water-bath under nitrogen, whereupon it was allowedto cool. 0.57 ml. of pyridine were added and it was heated for 1 hour onthe water-bath. It was cooled to 0° and diluted with a cold 10% HClsolution until a distinctly acid mixture was obtained. It was extractedwith 2 portions of petroleum ether (b.p. 30°-50°) and the extracts werewashed in the following manner: 10% HCl (at 0°), 5% NaHCO₃, water. Afterdrying over anhydrous Na₂ SO₄ it was concentrated and the residuedistilled under a high vacuum. There was thus obtained 0.31 g. (31.3%)of trans-2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene. The analyticalsample, purified by preparative gas chromatography had the followingphysical constants: IR spectrum: 1670, 1635, 1610, 970 cm⁻. Massspectrum: m/e: 69-121, 105, 41, 190. NMR spectrum: δ=1.01 ppm, (6 H, s);1.62 ppm, (3 H, s); 1.93 ppm, (3 H, d of d, J=6.5 cps and 1.5 cps); 2.07ppm, (2 H, d, J=2.3 cps); 5.77 ppm, (2 H, t, J=2.3 cps); 6.06 ppm, (1 H,d of q, J=16 cps and 1.5 cps); 6.75 ppm, (1 H, d of q, J=16 cps and 6.5cps).

EXAMPLE 15 Trans-2,6,6-trimethyl-1-crotonoyl-2-cyclohexane

A solution containing 2.8 g. of epoxy-α-jonone (Helv. Chim. Acta 29,1829 (1946) in 15 ml. of absolute methanol was cooled and 2.5 g. ofhydrazine hydrate were added under nitrogen with stirring, followed by0.3 g. of acetic acid. The temperature was maintained between 10 and 20°and an evolution of nitrogen was observed. When the evolution ofnitrogen was finished, the solution was diluted with water, neutralisedand extracted by the usual means. After drying and evaporation of thevolatile portions the extract yielded 2.4 g. of an oily liquid which wassubjected to a fractional distillation. The second fraction of thedistillation contained a 1:1 mixture of cis- and trans-2,6,trimethyl-1[1-hydroxy-2-butenyl]-2-cyclohexene. 100 mg. of thisdistillate were dissolved in 15 ml. of acetone and this mixture wasstirred for 60 hours at room temperature with 2 g. of MmO₂. The mixturewas filtered and the precipitate rinsed twice with ether. Afterconcentration of the solution and the rinsing fractions in vacuo amixture of cis- and trans-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene wasobtained which was purified by preparative gas chromatography. The twoisomeric ketones were thus separated and the constants thereof wereidentical to those described in Examples 20 hereinafter and 12respectively.

EXAMPLE 16 2,6,6-Trimethyl-1-crotonoyl-1-cyclohexene

(a) 426 g. of 2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]1-cyclohexaneprepared according to the method described in paragraph (b) herebelowwere mixed with 3.9 kg. of MnO₂ in 8 liter of petroleum-ether (b.p.30-50°). The mixture was stirred for 21/2 days at room temperature. Thesolvent was removed under vacuum and the crude2,6,6-trimethyl-1-crotonoyl1-cyclohexene (358 g.) which was left as theresidue of evaporation was used without further purification. The crudeketone which was mainly the cis-isomer, according to the vapour phasechromatographic analysis was isomerised to the trans-ketone by means ofp-toluensulfonic acid according to the process described in Example 19hereinafter. After isomerisation the resulting trans-ketone was purifiedby fractional distillation, b.p. 84°-85° /0.001 Torr.

The carbinol used as starting material in the preparation describedabove can be prepared as follows:

(b) 2,6,6-Trimethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene

In an atmosphere of nitrogen, a solution of 280 g. of 1-bromopropene in430 ml. of tetrahydrofuran was added dropwise at 63-65° into asuspension of 53.3 g. of magnesium turnings in 660 ml. oftetrahydrofuran. During the addition the reflux condenser fitting thereaction vessel was cooled to -40 to -50° in order to prevent escapingof the vapours of unreacted 1-bromopropene. The mixture was stirred foran additional 21/2 hours at 6°-62° after which it was cooled to 0°. Asolution of 278 g. of 62-cyclocitral in 350 ml. of tetrahydrofuran wasthen added dropwise between 0 and 7°. The mixture was allowed to standovernight then it was poured onto a mixture of ice and saturated aqueousNH₄ Cl solution. The organic layer was removed and the aqueous phaseextracted with petroleum-ether (b.p. 30°-50°). The combined extractswere washed as usual, dried and then evaporated under vacuum. Theresidue gave 350 g. of crude2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene which was usedwithout further purification.

EXAMPLE 17 2,6,6-Trimethyl-1-Trimethyl-1-crotonoyl-1,3-cyclohexadiene

The following ingredients were stirred at 51°-53° under an atmosphere ofnitrogen: 2,6,6-trimethyl-1-crotonoyl-1-cyclohexene prepared accordingto Example 16 (50 g.), N-bromosuccinimide (60.5 g.), CCl₄ (400 ml.), CH₂Cl₂ (200 ml.) and α,α'-azo-bis-isobutyronitrile (0.2 g.). The mixtureturned progressively red and started abruptly to boil violently. Theheat source was removed and the reaction rate was controlled by means ofa cooling bath. After about 10 minutes the reaction mixture becamecolourless. It was cooled to 20° and 89.5 g. of diethylamine and 800 ml.of petroleum-ether (b.p. 30°-50°) were added to it. Succinimide wasfiltered off, volatile solvents were removed under vacuum and theresidue was heated to 135°-140° for 21/2 hours. After cooling, themixture was stirred vigorously with 500 ml. of ice-cold 10% HCl. Themixture was extracted with petroleum ether and the extract was washedwith 5% HCl, concentrated aqueous NaHCO₃ and finally with water. Afterdrying over Na₂ SO₄ the extract was distilled to give 37 g. (75%) ofpure 2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene b.p. 46°/0.001 Torr.

EXAMPLE 18 Cis-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene

(a) A solution of 2,6,6-trimethyl-1 -tetrolyl-1-cyclohexene preparedaccording to the description of paragraph (c) herebelow (5 g.) in 50 ml.of petroleum-ether (b.p. 30°-50°) and 2 g. of Lindlar catalyst(deactivated Pd/C catalyst) prepared according to Helv. Chim. Acta 35,446 (1952) were placed in an apparatus for catalytic hydrogenations. Theabove mixture was hydrogenated at room temperature until 1 equivalent ofhydrogen had been used. The solution was filtered and the solventremoved in vacuo. Distillation of the residue gave 4.3 g. ofcis-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene, b.p. 82°-85°/0.001 Torrthe constants of which were the same as those described in Example 13.

The acetylenic ketone used as starting material in the above preparationwas prepared as follows:

(b) 2,6,6-Trimethyl-1-[1-hydroxy-2-butynyl]-1-cyclohexene

Under an atmosphere of nitrogen 56 mMole of methyllithium in about 30ml. of ether were added to 100 ml. of dioxane. The mixture was stirredvigorously and, between 0° and 10°, 2.47 g. (61.6 mMole) of propyne wereadded to it. The vapours of the propyne which did not immediately reactwere condensed in a condenser cooled with liquid nitrogen. The unreactedpropyne was thus continuously returned to the reaction vessel. When allpropyne had reacted (approx. 30-60 minutes) a solution of 7.6 g. (50mMole) of β-cyclocitral in 10 ml. of ether was added dropwise at roomtemperature. After stirring for an additional 10-12 hours the mixturewas poured onto ice, neutralised with NH₄ Cl and extracted withpetroleum-ether. The extract was washed and dried by usual means, thenit was concentrated under reduced pressure. Distillation of the residuegave 6.6 g. of 2,6,6-trimethyl-1-[1-hydroxy-2-butynyl]- 1-cyclohexene,b.p. 95-97°/0.7 Torr, as a colourless viscous oil.

(c) Oxidation 2,6,6-trimethyl-1-[1-hydroxy-2-butynyl-]-1-cyclohexene

A mixture of 1.277 g. (66.3 mMole) of the acetylenic carbonyl compoundprepared according to the description of paragraph (b) above, 12 g. ofactivated HnO₂ and 100 ml. of petroleum-ether (30°-40°) were stirred for15 minutes at room temperature. The solid was removed by filtration andthe liquid was dried over molecular sieves then it was concentrated anddistilled under reduced pressure. 1.02 g. (81%) of2,6,6-trimethyl-1-tetrolyl-1-cyclohexene were thus obtained, theanalytical measurements thereof gave the following results: n_(D) ²⁰=1.5107; d₄ ²⁰ =0.957. IR spectrum (liquid phase); 2210 (ν_(C).tbd.C),1640 (ν_(C)═O) cm⁻¹. NMR spectrum (CCl₄): 1.08 (3 H, s), 1.68 (3 H, s),2.02 (3 H, s) ppm (δ). Mass spectrum: 190 (28), 175 (100), 67 (63), 123(37), 41 (25), 81 (24), 135 (22), 28 (21), 91 (20), 147 (20).

EXAMPLE 19 Trans-2,6,6-trimethyl-1-crotonyl-1-cyclohexene

Under an atmosphere of nitrogen, a solution containing 1.16 g. ofcis-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene prepared according toExample 18, 12 ml. of dry benzene and 0.023 g. of p-toluenesulfonic acidwere stirred 48 hours at room temperature. The solution was diluted withether, neutralised and washed as usual. The volatile components wereremoved in vacuo and distillation gave a 90% yield oftrans-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene, b.p. 78°-80°/0.001Torr, the constants of which were found identical with those of thecompound described in Example 12.

EXAMPLE 20 Cis-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene

(a) 2,6,6-Trimethyl-1-tetrolyl-2-cyclohexene obtained according to thedescription of paragraph (c) herebelow was hydrogenated according to themethod described in Example 18, paragraph (a). Thus,cis-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene was obtained in 85-00%yield. The spectral characteristics were as follows: NMR spectrum(CCl₄): 0.85 (3 H, s); 0.96 (3 H, s), 1.62 (3 H, s broad), 2.12 (3 H, d,J=5.5 cps), 1.0-2.3 (4 H, complex band), 2.95 (1 H, s broad), 5.49 (1 H,s broad), 6.25 (2 H, complex band) ppm (δ).

The acetylenic ketone used as starting material in the above preparationcan be prepared as follows:

(b) 2,6,6-Trimethyl-1-[1-hydroxy-2-butynyl]-2-cyclohexene

Following the procedure described in Example 18 3 g. of α-cyclocitralwere reacted wth propyne to give 2.0 g. (79%) of2,6,6-trimethyl-1-[1-hydroxy-2-butynyl]-2-cyclohexene, b.p. 85°-87°0.8Torr. IR spectrum (liquid phase): 3460 (ν_(OH)), 2200 (ν_(C).tbd.C) 1660(ν_(C)═C) cm⁻¹. NMR spectrum (CDCl₃): 0.88 (3 H, s), 1.05 (3 H, s), 1.84(3 H, m), 1.97 (3 H, s), 5.76 (1 H, m) ppm (δ).

(c) Oxidation of 2,6,6-trimethyl-1-[1-hydroxy-2-butynyl]-2-cyclohexene

The acetylenic carbinol which was obtained as described above underparagraph (b) was oxidised as described for its isomer in Example 18,paragraph (c). Thus, 1.38 g. of carbinol gave 0.9 g. (66%) of2,6,6-trimethyl-1-tetrolyl-2-cyclohexene, b.p. 100°-105°/0.7 Torr. NMRspectrum (CCl₄): 0.96 (6 H, d badly resolved), 1.52 (3 H, m), 2.0 (3 H,s), 5.57 (1 H, m), 2.66 (1 H, m) ppm (δ).

EXAMPLE 21 2,6,6-Trimethyl-1-crotonoyl-2-cyclohexene

Under an atmosphere of nitrogen, 0.5 Mole of lithium α-cyclogeraniateand 6.9 g. (1 Mole) of lithium cut into small pieces were suspended in 1liter of ether. At room temperature a solution of 0.5 Mole of1-bromopropene in 250 ml. of ether was added dropwise. Stirring wascontinued for 24 hours then the whole mixture was poured into an excessof an ice-cold saturated solution of NH₄ Cl and stirred vigorously. Theorganic layer was separated and treated as usual. Distillation of theresidue resulting from the removal of the volatile components gave a 36%yield of 2,6,6-trimethyl-1-crotonoyl-2-cyclohexene.

EXAMPLE 22 Trans-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene

(a) A mixture of 10 g. of 6,10-dimethyl-4-oxo-2,5,9-undecatrieneprepared according to the method of paragraph (c) herebelow, 100 ml. ofbenzene and 1 g. of boron trifluoride etherate was heated to the refluxuntil the vapour phase chromatographic analysis of a sample showed thatpractically all the starting material had disappeared. The solution wascooled and stirred with ice-water. The organic layer was removed andtreated as usual. Distillation of the residue of evaporation gave a 50%yield of trans-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene of about 60%purity as shown by the vapour phase chromatographic analysis.

The ketone used as starting material in the above preparation can beprepared as follows:

(b) 6,10-Dimethyl-4-hydroxy-2,5,9-undecatriene

12 g. of magnesium turnings were suspended under nitrogen in 250 ml. ofdry tetrahydrofuran. Between 60° and 65°, 60 g. of 1-bromopropenedissolved in 50 ml. of tetrahydrofuran were added dropwise. During theaddition, to prevent escaping of 1-bromopropene, the reflux condenserfitted on the reaction flask was cooled to -40°/-50°. When all Mg hadreacted, the mixture was cooled to 20° and 76 g. of citral was addeddropwise with cooling. After standing overnight, the mixture was pouredinto 1.5 liter of concentrated aqueous NH₄ Cl at 0°. The mixture wasextracted 3 times with ether and the combined ether extracts treated asusual. After distillation, 6,10-dimethyl-4-hydroxy-2,5,9-undecatriene,b.p. 70°/0.1 Torr was obtained as a liquid with following constants:n_(D) ²⁰ =1.4950; d₄ ²⁰ =0.9145. (c)6,10-Dimethyl-4-oxo-2,5,9-undecatriene

60 g. of the alcohol prepared according to paragraph (b) above, 700 g.of MnO₂ and 1800 ml. of CH₂ Cl₂ were stirred for 2 days at 20°-25°.After filtration and evaporation, the distillation of the residue gave49 g. of crude ketone, b.p. 70°-75°/0.1 Torr. which was purified byvapour phase chromatography using a "20 M Carbowax" column and heliumcarrier at 140°. n_(D) ²⁰ =1.5041; d₄ ²⁰ =0.8958.

EXAMPLE 23 Cis-2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene

Safranal, prepared according to Compt. rend. 262, 1725 (1966), wasreacted with propyne to give2,6,6-trimethyl-1-[1-hydroxy-2-butynyl]-1,3-cyclohexadiene, followingthe procedure outlined in Example 18, paragraph (b), for the reaction ofcitral with propyne. The above carbinol was oxidised with MnO₂ to2,6,6-trimethyl-1-tetrolyl-1,3-cyclohexadiene, following the proceduredescribed in Example 18, paragraph (c), for the oxidation of the dihydroanalogue. The above acetylenic ketone was then partially reduced to thetitle compound folowing the method described in Example 18, paragraph(a). Cis-2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene gave thefollowing NMR data (CCl₄): 1.06 (6 H, s) 1.69 (3 H, s), 2.09 (2 H, d,J=2.3 cps.), 2.14 (3 H, d, J=5.5 cps), 5.81 (2 H, t+s, J=2.3 cps), 6.2(2 H, complex band) ppm (δ).

EXAMPLE 24 2,6,6-Trimethyl- 1-[2-penteneyl]-2-cyclohexene

(a) 7,11-Dimethyl-5-oxo-3,6,10-dodecatriene (75 g.), containing a smallamount of 7,11-dimethyl-5-oxo-3,6,10-dodecatriene and11-methyl-7-methylene-5-oxo-3,10-dodecadiene, was added dropwise at0°-5° under nitrogen to a vigorously stirred solution of tin chloride(30 g.) in 350 ml. of dry benzene.

The reaction mixture kept at 30°-35° was stirred until the analysis byvapour phase chromatography revealed complete disappearance of startingtrienes (2-3 h.). It was then poured into crusched ice, extracted withether and the extracts were combined and washed with water until theywere neutral to litmus. After drying, the volatile portions wereevaporated and the residue (72 g.) distilled. 22.6 g. (30% yield) oftrans-2,6,6-trimethyl-1-[2-pentenoyl]-2-cyclohexene, B.p. 75°-7°/0.1Torr, were thus obtained. n_(D) ²⁰ =1.4925; d₄ ²⁰ =0.9281.

7,11-Dimethyl-5-oxo-3,6,10-dodecatriene used as starting material wasprepared as follows:

(b) Dehydrolinalool (456 g; 3 Mole) was added at 20° to a freshlyprepared solution of KOH (220 g.; 3.9 Mole), K₂ CO₃ (30 g.) and Cu₂ Cl₂(20 g.) in 1500 ml. of methanol. To this solution 3-chloro-1-butene (352g.; 3.9 Mole) was then added dropwise with vigorous stirring while thetemperature was kept below 50°. Stirring was continued for 3 h. and theresidue obtained by evaporating the methanol under reduced pressure wasthoroughly mixed with 1 l. of water. This mixture was extracted withether and after the usual treatments gave by distillation, together with44 g. of dehydrolinalool, 530 g. of a 85:15 mixture of7,11-dimethyl-2,10-dodecadiene-5-yn-7-ol (A) and3,6,10-trimethyl-1,9-undecadiene-4-yn-6-ol (B). These two alcohols wereseparated by distillation using a spinning band column, and showed thefollowing analytical constants:

Compound A (400 g.): B.p. 84°-5°/0.1 Torr; n_(D) ²⁰ = 1.4824; d₄ ²⁰ =0.8872.

IR spectrum: 3380, 2235 and 960 cm⁻¹.

Compound B (80 g.): B.p. 80°/0.1 Torr: n_(D) ²⁰ = 1.4789; d₄ ²⁰ =0.8944. IR spectrum: 3380, 2235, 1640 and 915 cm⁻¹.

(c) 400 g. of compound A prepared according to paragraph (b) were heatedduring 3 h. at 130° in the presence of 700 g. of acetic anhydride and 60g. of sodium acetate. The excess of anhydride was then distilled off at50° under reduced pressure and the residue was treated with water.

This mixture was extracted with petrol-ether, washed with a solution ofsodium carbonate and after the usual treatments gave by distillation 414g. (90% yield) of the acetate of alcohol A which showed the followinganalytical constants: B.p. 88°-90°/0.1 Torr; n_(D) ²⁰ = 1.4732; d₄ ²⁰ =0.9122. IR spectrum: 2240, 1740 and 965 cm⁻¹.

(d) 248 g. of the acetate prepared according to paragraph (c) wereheated at 90° during 5 h. in the presence of 500 ml. of acetic acid and10 g. of copper acetate. By means of vapour phase chromatography it wasshown that the starting acetate had completely reacted. The mixture wasconcentrated in vacuum and the residue was treated with 300 ml. ofwater. After extraction with petrol-ether and the usual treatments, 190g. of a mixture consisting of 7,11-dimethyl-5-oxo-3,6,10-dodecatrieneand two isomeric ketones, 7,11-dimethyl-5-oxo-3,7,10-dodecatriene and11-methyl-7-methylene-5-oxo-3,10-dodecadiene, were obtained.

Such a mixture, used directly for the cyclisation process described inparagraph (a), had the following analytical constants: B.p. 88°-97°/0.1Torr; n_(D) ²⁰ = 1.4932; d₄ ²⁰ = 0.8919.

EXAMPLE 25 2,6,6-Trimethyl-1-[2-methylcrotonoyl]-2-cyclohexene

(a) 3,6,10-trimethyl-4-oxo-2,5,9-undecatriene (25 g.), containing asmall amount of isomeric ketones3,6,10-trimethyl-4-oxo-2,6,9-undecatriene and3,10-dimethyl-6-methylene-4-oxo-2,9-undecadiene, was subjected tocyclisation according to the same procedure described in paragraph (a)of Example 24, in the presence of 50 ml. of dry benzene and 10 g. ofSnCl₄. By distillation of 22 g. of crude product, 12.8 g. of an oilysubstance were obtained. A purification by means of vapour phasechromatography gave 8.8 g. of2,6,6-trimethyl-1-[2-methylcrotonoyl]-2-cyclohexene, the analyticalconstants of which are: B.p. 70°-1°/0.1 Torr; n_(D) ²⁰ = 1.4818; d₄ ²⁰ =0.9249.

IR spectrum: 1720, 1630, 825, 810 cm⁻¹.

The mixture of the ketones used as starting materials in the abovepreparation was obtained as follows:

(b) The alcohol B (50 g.), obtained according to the procedure describedin paragraph (b) of Example 24 was acetylated by means of aceticanhydride (84 g.) in the presence of sodium acetate (8 g.) as describedin paragraph (c) of Example 24. 54 g. (90% yield) of the acetate of3,6,10-trimethyl-1,9-undecadiene-4-yn-6-yl were thus obtained. IRspectrum: 2245, 1745, 1640 and 915 cm⁻¹.

(c) 37 g. of the acetate prepared according to the method describedabove were heated at 90° during 5 h. in the presence of 75 ml. of aceticacid and 1.5 g. of copper acetate.

26 g. (85% yield) of 3,6,10-trimethyl-4-oxo-2,5,9-undecatriene togetherwith two other isomeric ketones, were thus obtained. This mixture wasdirectly used for the cyclisation reaction according to paragraph (a).

The mixture had the following analytical constants: B.p. 75°-7°/0.1Torr; n_(D) ²⁰ = 1.4889; d₄ ²⁰ = 0.8890.

EXAMPLE 26 2,6,6-Trimethyl-1-[3-methylcrotonoyl]-2-cyclohexene

(a) 2,6,10-trimethyl-4-oxo-2,5,9-undecatriene (20 g.) was cyclisedaccording to the procedure described in paragraph (a) of Example 24 inthe presence of 7 g. of SnCl₄ in 100 ml. of dry benzene. During theaddition of the ketone, the temperature was kept below 150° then it wasdecreased at 40° while the stirring was continued for 4 hours. Accordingto the usual procedure, 6.8 g. (34% yield) of pure product wereobtained.

B.p. 67°-8°/0.1 Torr; n_(D) ²⁰ = 1.4818; d₄ ²⁰ = 0.9249.

IR spectrum: 1670, 1615, 826 and 805 cm⁻¹.

The starting material accompanied by the isomeric ketones2,6,10-trimethyl-4-oxo-2,6,9-undecatriene and2,10-dimethyl-6-methylene-4-oxo-2,9-undecadiene was obtained accordingto:

(b) Methallyl chloride (100 g.) was added portion-wise under nitrogen toa solution of KOH (60 g.), K₂ CO₃ (10 g.) and Cu₂ Cl₂ (7 g.) in 500 ml.of methanol. During the addition, the temperature was kept at ca. 40°.The stirring was maintained for 3 more hours then, after evaporation ofthe volatile components, the residue was treated with 500 ml. of waterand 300 ml. of petrol-ether. The extracts were purified and treatedaccording to paragraph (b) of Example 24.

152 g. (90% yield) of 2,6,10-trimethyl-2,10-undecadiene-7-yn-6-oltogether with 35 g. of dehydrolinalool were obtained. B.p. 70°-2°/0.1Torr; n_(D) ²⁰ = 1.4818, d₄ ²⁰ = 0.8941. IR spectrum: 3350, 2245, 1650and 890 cm⁻¹.

(c) 105 g. of the alcohol prepared according to paragraph (b) wereacetylated with 200 g. of acetic anhydride and 20 g. of sodium acetateaccording to the procedure described in paragraph (c) of Example 24. 112g. (90% yield) of the corresponding acetate were thus obtained. B.p.80°/0.01 Torr; n_(D) ²⁰ = 1.4709; d₄ ²⁰ = 0.9173.

IR spectrum: 2245, 1740, 1645, 890 cm⁻¹.

(d) 248 g. of the acetate prepared according to paragraph (c) wereisomerised by acetic acid (400 ml.) and coopper acetate (15 g.). 187 g.of a mixture containing 2,6,10-trimethyl-4-oxo-2,5,9-undecatriene andtwo other isomeric ketones were obtained according to the same proceduredescribed in paragraph (d) of Example 24.

B.p. 90°-7°/0.1 Torr; n_(D) ²⁰ = 1.5075; d₄ ²⁰ = 0.8915.

EXAMPLE 27 Trans-2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene

A mixture of cis- andtrans-2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane (10 g.) obtainedaccording to Example 28 and 2 g. of acid diatomaceous earth in 50 ml. ofdioxan was kept under nitrogen at 100°-105° until completetransformation of the starting epoxides into2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene. The course of thereaction was followed by sample analysis at set time intervals, by meansof vapour phase chromatography. After filtration the filtrate wasdistilled to give 8.0 g. of product B.p. 60°-85°/0.5 Torr, thespectrometric analysis of which revealed a content of 7.5 g. (82%) of2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene.

IR: 1670, 1635, 1610, 970 cm⁻¹.

NMR: 1.01 (6 H, s); 1.62 (3 H, s); 1.93 (3 H, d.d., J= 6.5 and 1.5 cps);2.07 (2 H, d, J= 2.3 cps); 5.77 (2 H, t, J= 2.3 cps); 6.06 (1 H, d.q.,J= 16 and 1.5 cps); 6.75 (1 H, d.q. J= 16 and 6.5 cps) δ ppm.

MS: m/e 69-121, 105, 41, 190

The reaction above proceeds through the formation of an hydroxyintermediate, 2,6,6-trimethyl-1-hydroxy-1-crotonoyl-2-cyclohexene, whichwas isolated by v.p.c. and showed the following analytical data:

IR: 3090, 1675, 1620, 970 cm⁻¹.

NMR: 0.72 (3 H, s); 0.97 (3 H, s); 1.45 (3 H, m); 1.92 (d, J= 7.5 cps),4.07 (1 H, m); 5.7 (1 H, m); 6.35-7.2 (2 H, m) δ ppm.

MS: M⁺ = 208 (0.1); m/e= 190 (0.1); 175 (0.1); 165 (0.1); 152 (0.1);(139 (49); 121 (3); 109 (2); 95 (33); 82 (3); 69 (28); 55 (7); 43 (100);27 (5).

EXAMPLE 28 Cis- andtrans-2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane

2,6,6-Trimethyl-1-vinylacetyl-1,2-epoxycyclohexane (10 g., 95% pure) and1 g. of sodium acetate in 50 ml. of dioxan were heated at 100° untilcomplete transformation of the starting epoxyde into2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane, the course of thereaction being followed by v.p.c. (Carbowax or Silicone, 180°, 3 m). Twohours are usually required for such a reaction.

After cooling and filtration, the distillation of the mixture gave 9.8g. of a mixture of the cis- (90%) and trans- (10%) isomers.

V.p.c. enabled the separation of the two isomeric compounds:

trans-2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane

B.p. 80°/0.5 Torr; n_(D) ²⁰ = 1.4861; d₄ ²⁰ = 0.9849.

C₁₃ H₂₀ O₂ Calc.ed: C 74.96; H 9.68%. Found: C 75.02; H 9.64.

IR: 1700-1620, 968 cm⁻¹.

NMR: 1.0 and 1.06 (6 H, 2 s); 1.08 (3 H, s); 1.92 (3 H, d, J= 7 cps);6.1-7.2 (2 H, m) δ ppm.

MS: M⁺ = 208 (0.1); m/e= 193 (0.1); 180 (0.1); 165 (0.1); 151 (5); 139(12); 125 (14); 111 (64); 95 (5); 82 (12); 69 (100); 55 (80); 41 (62);29 (8).

Cis-2,6,6 -trimethyl-1-crotonoyl-1,2-epoxycyclohexane

B.p. 79°/0.5 Torr; n_(D) ²⁰ = 1.4803; d₄ ²⁰ = 0.9833

C₁₃ H₂₀ O₂ Calc.ed: C 74.96; H 9.68%. Found: C 75.11; H 9.60.

IR: 1680, 1615, 748 cm⁻¹.

NMR: 1.00 and 1.07 (6 H, 2 s); 1.1 (3 H, s); 2.12 (3 H, d, J= 7 cps);6.0-6.57 (2 H, m) δ ppm.

MS: M⁺ = 208 (0.1); m/e: 193 (1); 175 (0.1); 165 (0.1); 151 (15); 135(2); 123 (9); 111 (6); 95 (4); 81 (2); 69 (100); 55 (18); 41 (26) 29(3).

EXAMPLE 29 2,6,6-Trimethyl-1-vinylacetyl-1,2-epoxycyclohexane

A solution of2,6,6-trimethyl-1-[1-hydroxy-3-butenyl]-1,2-epoxycyclohexane (178.5 g.),obtained according to Example 30, in 265 ml. of toluene was addeddropwise with vigorous stirring to a solution of Na₂ Cr₂ O₇ (620 g.) in500 ml. of conc. H₂ SO₄ and 1220 ml. of water at 0°-5°. At the sametemperature the mixture was kept during 3 h., extracted with ether togive, after the usual treatments, 114.7 g. (67%) of crude product whichafter distillation, b.p. 78°/0.4 Torr, gave 100 g. (59%) of an oil. Thev.p.c. analysis showed that this oil had a 95% content of2,6,6-trimethyl-1-vinylacetyl-1,2-epoxycyclohexane, n_(D) ²⁰ = 1.4721;d₄ ²⁰ = 0.9781.

C₁₃ H₂₀ O₂ Calc.ed: C 74.96; H 9.68%. Found: C 74.66; H 9.72.

IR: 3080, 1820, 1700, 1640, 915, 910 cm⁻¹.

NMR: 1.02 and 1.05 (6 H, 2 s); 1.1 (3 H, s); 3.2 (2 H, m); 4.8-6.2 (3 H)δ ppm.

MS: M⁺ = 208 (0.1); m/e: 193 (1); 177 (1); 165 (0.1); 151 (15); 135 (2);123 (8); 111 (4); 95 (3); 81 (2); 69 (100); 55 (18); 41 (29).

EXAMPLE 30 2,6,6-Trimethyl-1-[1-hydroxy-3-butenyl]-1,2-epoxycyclohexane

A mixture of 40% peracetic acid (105 g.) and anhydrous sodium acetate(3.0 g.) was added at 25° with stirring to a suspension of2,6,6-trimethyl-1-[1-hydroxy-3-butenyl]-1-cyclohexene (97 g.) and anhyd.sodium acetate (60 g.) in 175 ml. of CH₂ Cl₂ (1.5 h.). Stirring wascontinued for one night and 500 ml. of water were then added to thereaction mixture. The organic layer was separated and, after the usualtreatments, distilled to give 98 g. (83%) of two diastereoisomers of theepoxy product.

V.p.c. enabled the separation of the two isomers (Carbowax, 170°, 3 m)

Peak 1: (80%), b.p. 88°-9°/0.5 Torr; n_(D) ²⁰ = 1.4790; d₄ ²⁰ = 0.9772

IR: 3540, 1820, 1640, 990, 900 cm⁻¹

NMR: 1.0 and 1.03 (6 H, 2 s); 1.42 (3 H, s); 2.52 (1 H, s); 3.92 (1 H,t); 4.7-6.4 (3 H) δ ppm.

MS: M⁺ = 210 (0.1); m/e: 192 (0.1); 177 (0.1); 169 (2); 149 (5); 140(3); 125 (22); 109 (28); 95 (12); 83 (23); 69 (46); 55 (36); 43 (100);27 (12).

Peak 2: (20 %), b.p. 93°-4°/0.5 Torr; n_(D) ²⁰ =1.4839; d₄ ²⁰ =0.9945

IR: 3095, 3060, 1635, 990, 910 cm⁻¹.

NMR: 1.00 and 1.16 (6 H, 2 s); 1.33 (3 H, s); 3.92 (1 H, m); 4.68-6.2 (3H) δ ppm.

MS: M⁺ =210 (0.1); m/e: 192 (0.1); 1.77 (0.1); 169 (2); 149 (5); 140(2); 119 (59); 109 (34); 95 (13); 83 (25); 69 (47); 55 (42); 43 (100 );27 (13).

2,6,6-Trimethyl-1-[1-hydroxy-3-butenyl]-1-cyclohexene used as startingmaterial in the above preparation, can be obtained as follows:

2,6,6-Trimethyl-1-[1-hydroxy-3-butenyl]-1-cyclohexene

5 g. of allyl chloride were added under nitrogen to a suspension ofmagnesium (28.8 g.) in 50 ml. dry ether. According to the procedurecommonly used for carrying out a Grignard reaction, allyl chloride (85g.) and β-cyclocitral (152 g.) in 350 ml. of dry ether were added atsuch a rate as to maintain the solvent at constant reflux.

At this temperature the mixture was stirred for 3 more hours and pouredthen into an NH₄ Cl aqueous solution.

The ethereal extracts gave by distillation, 178.1 g. (90 %) of thehydroxy-compound (97 % pure). B.p. 50°/0.01 Torr, n_(D) ²⁰ =1.4958; d₄²⁰ =0.9390.

EXAMPLE 31Trans-2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1,2-epoxycyclohexane

21 g. of 40 % percetic acid and 0.6 g. of sodium acetate were addedunder nitrogen to a suspension of2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1-cyclohexene (19.4 g.) and 12g. of sodium acetate in 35 ml. of CH₂ Cl₂ at 20°. The reaction mixturewas left 2 more hours with stirring and it was then poured into 250 ml.of water.

The organic layer gave by distillation 19.5 g. (93%) of epoxy product.B.p. 84°/0.1 Torr; n_(D) ²⁰ =1.4814; d₄ ²⁰ =0.9933.

C₁₃ H₂₂ O₂ Calc.ed: C 74.24; H 10.54% Found: C 73.67; H 10.40.

IR: 3090, 960 cm⁻¹.

NMR: 1.02 (6 H, s); 2.74 (1 H, m); 4.38 (1 H, m); 5.55 (2 H, m) δ ppm.

MS: M⁺ =210 (0.1); m/e: 192 (0.1); 177 (0.1); 168 (1); 149 (10); 140(39); 125 (93); 109 (16); 95 (14); 84 (24); 69 (49); 55 (50); 43 (10);29 (14).

EXAMPLE 32 Trans-2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane

A solution oftrans-2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1,2-epoxycyclohexane in 20ml. of toluene was added at 0°-5° with vigorous stirring to a solutionof Na₂ Cr₂ O₇ (31 g.) in 25 g. of conc. H₂ SO₄ and 60 ml. of water. Themixture was kept at 0°-5° during 3 h., then at room temperature duringone night. After addition of 250 ml. of water, the mixture was extractedwith 100 ml. of pet.-ether and the extracts evaporated. Distillation ofthe obtained residue gave a colourless oil (5.2 g.) and 6.1 g. ofresidue.

The v.p.c. analysis showed that the oil had a 4.5 g. (35%) content oftrans-2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane.

EXAMPLE 33 Trans-2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane

Trans-2,6,6-trimethyl-1-[1-hydroxy-2-butenyl]-1,2-epoxycyclohexane (2.1g.) and 20 g. of MnO₂ (freshly activated by heating it at 100°-105°during 1 h.) in 50 ml. of pet.-ether were mixed and allowed to react atroom temperature. The course of the reaction was followed by v.p.c.analysis of sample aliquots. After ca. 12 h., 70% of the startingalcohol was oxidised into the corresponding ketone.

After filtration, a novel portion of MnO₂ (10 g.) was added and the sameoperation was started again until obtainment of 90% of the desiredketone. By distillation 1.9 g. of product were obtained:

1.2 g. (60%) of trans-2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane

0.15 g. (8%) of starting material

0.55 g. of by-products.

EXAMPLE 34 2,6,6-Trimethyl-1-[1-hydroxy-3-butenyl]-2-cyclohexene

Allyl chloride (5 ml.) was added under nitrogen to a suspension ofmagnesium (28.8 g.) in 300 ml. of dry ether. According to the usualprocedure of a Grignard reaction, allyl chloride (85 g.) andα-cyclocitral (152 g.) in 100 ml. of dry ether were added at such a rateas to maintain the solvent at reflux. At this temperature, the mixturewas left during 3 h. and poured then into an NH₄ Cl aqueous solution.

The ethereal layer gave by evaporation and subsequent distillation 182g. (95%) of a mixture of the two diastercoisomers of the hydroxycompound: V.p.c. (Carbowax, 170°, 3 m) enabled the separation of the twoisomers:

Peak 1: ca. 70%; b.p. 62°/0.1 Torr, n_(D) ²⁰ =1.4878; d₄ ²⁰ =0.9276

C₁₃ H₂₂ O Calc.ed: C 80.35; H 11.44% Found: C 79.87; H 11.26.

IR: 3400, 3060, 1820, 1635, 988, 910 cm⁻¹.

NMR: 0.85 and 0.98 (6 H, 2 s); 1.75 (3 H, s); 3.75 (1 H, t); 5.6 (1 H,m); 4.88-6.0 (3 H) δ ppm.

The mass spectrum was practically identical to that of the productcorresponding to peak 2.

Peak 2: ca. 30 %; b.p. 62°/0.1 Torr; n_(D) ²⁰ =1.4922; d₄ ²⁰ =0.9319

C₁₃ H₂₂ O Calc.ed: C 80.35; H 11.44% Found: C 79.91; H 11.19%

IR: 3420, 3070, 1815, 1630, 985, 910 cm⁻¹.

NMR: 0.91 and 1.05 (6 H, 2 s); 1.78 (3 H, m); 4.82 (m); 5.45 (1 H, m);4.86-6.2 (3 H) δ ppm.

MS: M⁺ =194 (0.1); m/e: 176 (0.1); 161 (0.1); 153 (2); 135 (2); 124(64); 109 (100); 95 (13); 81 (27.5); 68 (31); 55 (10); 41 (30); 27 (8).

EXAMPLE 35 2,6,6-Trimethyl-1-vinylacetyl-2-cyclohexene

A solution of 2,6,6-trimethyl-1-[1-hydroxy-3-butenyl]-2-cyclohexene(191.4 g.), prepared according to Example 34, in 310 ml. of toluene wasadded dropwise with vigorous stirring at 0°-5° to a solution of Na₂ Cr₂O₇. 2 H₂ O (365 g.) in 300 g. of conc. H₂ SC₄ and 1800 ml. of water (1.5h.).

The reaction mixture was left at room temperature during 10 h. and,after separation of the organic phase, 300 ml. of pet.-ether were addedto it.

The combined organic extracts gave after the usual treatments anddistillation 170 g. of a product b.p. 50°-3°/0.1 Torr, which had a 90%content of 2,6,6-trimethyl-1-vinylacetyl-3-cyclohexene. Yield ca. 80%.

A sample purified by v.p.c. showed the following analytical data:

B.p. 53°/0.1 Torr; n_(D) ²⁰ =1.4830; d₄ ²⁰ =0.9371.

C₁₃ H₂₀ O Calc.ed: C 81.20; H 10.48% Found: C 80.21; H 10.43.

IR: 3080, 1820, 1710, 1640, 990, 900, 808 cm⁻¹.

NMR: 0.88 and 0.93 (6 H, 2 s); 1,58 (3 H, s); 3.17 and 3.27 (2 H, 2 m);5.55 (1 H, m); 4.85-6.3 (3 H) δ ppm.

MS: M⁺ =192 (5); m/e: 177 (0.1); 166 (0.1); 151 (12); 135 (1); 123(100); 107 (6); 95 (10); 81 (80); 69 (60); 55 (10); 41 (44); 27 (5).

EXAMPLE 36 Trans-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene

2,6,6-Trimethyl-1-vinylacetyl-2-cyclohexene (170 g.), obtained accordingto Example 35, was heated during 1 h. with ca. 1 ml. of conc. HCl in 500ml. of tetrahydrofuran. The solution was concentrated in vacuo to avolume of ca. 300 ml., then 300 ml. of pet.-ether and 300 ml. of adiluted NaHCO₃ solution were added to it.

The organic phase gave, after the usual treatments, 168 g. of a product,b.p. 52°-55°/0.1 Torr, which had a 92% content oftrans-2,6,6-trimethyl-1-crotonoyl-2-cyclohexene.

NMR: 0.85 and 0.96 (6 H, 2 s); 1.62 (3 H, s); 2.12 (3 H, d, J=5.5 cps);1.0-2.3 (4 H, complex band); 2.95 (1 H, s); 5.49 (1 H, s); 6.25 (2 H,complex band) δ ppm.

EXAMPLE 37 2,6,6-Trimethyl-1-hydroxy-1-crotonoyl-2-cyclohexene

A mixture of the cis- and trans-isomers of2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane (10 g.) [cf. Example32] and 2 g. of acid diatonaceous earth in 50 ml. of dioxan was heatedunder nitrogen at 100°-105°.

The course of the reaction was followed by v.p.c. analysis of samplealiquots taken at set time intervals. After filtration and purification,the product had the following analytical data:

n_(D) ²⁰ =1.5049; d₄ ²⁰ =1.018

C₁₃ H₂₀ O₂ Calc.ed: C 74.96; H 9.68% Found: C 74.68; H 9.69%.

IR: 3090, 1675, 1620, 970 cm⁻¹.

NMR: 0.72 and 0.97 (6 H, 2 s); 1.45 (3 H, m); 1.92 (d, J=7.5 cps), 4.07(1 H, m); 5.7 (1 H, m); 6.35-7.2 (2 H, m) δ ppm.

MS: M⁺ =208 (0.1), m/e: 190 (0.1); 175 (0.1); 165 (0.1); 152 (0.1); 139(49); 121 (3); 109 (2); 95 (33); 82 (3); 69 (28); 55 (7); 43 (100); 27(5).

EXAMPLE 38 Aromatization of corn-syrup

A base composition of corn-syrup was aromatized by the addition of2,6,6-trimethyl-1-hydroxy-1-crotonoyl-2-cyclohexene, as uniqueingredient, in the proportion of 0.03 g. of a 1% solution in 95% alcoholfor 100 ml. of base syrup.

The syrup thus obtained, contrary to the base syrup which had a blandtaste, possesses a taste of honey and a light flavour note which remindsof roasted hazelnuts.

EXAMPLE 39 Aromatization of black-tea

A test solution of black tea was obtained by brewing during 5 minutes 6g. of bland taste black-tea leaves of commercial quality in 600 ml. ofboiling water. When to 100 ml. of this solution 0.05 g. of a 1% solutionof 2,6,6-trimethyl-1-crotonoyl-2,3-epoxycyclohexane in 95% alcohol wereadded, a solution with a more herb-like note which distinctly remindedof camomile was obtained.

EXAMPLE 40 Perfume composition of Chypre type

A perfume composition of Chypre type was obtained by admixing thefollowing ingredients (parts by weight):

    ______________________________________                                        Bergamot                    21                                                Portugal                    0.5                                               Synthetic Neroli            1                                                 Synthetic rose              9                                                 Synthetic Jasmine           9                                                 Ylang extra                 6                                                 Methylionone                6                                                 Hydroxycitronellal          6                                                 Oriental santal             3                                                 Patchouli                   1.5                                               Vetyveryl acetate           4.5                                               Natural degreased civet 10% sol.*                                                                         3                                                 Ciste labdanum absolute 10% sol.*                                                                         2                                                 Musk ketone                 4                                                 1,1-Dimethyl-6-tert. butyl-4-acetyl-indane                                                                0.5                                               Coumarin                    3                                                 Trichloromethylphenylcarbinyl acetate                                                                     1.5                                               Tarragon 10% sol.*          3                                                 Oak moss absolute 50% sol.* 6                                                 Benjoin resin 10% sol.*     1.5                                               Styrax cinnamic alcohol     1.5                                               Jasmine absolute            1.5                                               Rose absolute               1                                                 Cyclopentadecanolide 10% sol.*                                                                            2                                                 Methylnonylacetic aldehyde  1.5                                               ______________________________________                                         *in diethyl phthalate                                                    

By adding to 99.5 g. of this mixture 0.5 g. (as a 10% solution indiethylphthalate) of cis- ortrans-2,6,6-trimethyl-1-crotonoyl-1,2-epoxycyclohexane the compositionobtained was more powerful than the basic composition and had improveddiffusion as well as a very natural richness.

EXAMPLE 41 Perfume composition of the chypre type

A chypre type composition was prepared by mixing the followingingredients (parts by weight):

    ______________________________________                                        Bergamot                    21                                                Portugal                    0.5                                               Synthetic Neroli            1                                                 Synthetic rose              9                                                 Synthetic Jasmine           9                                                 Ylang extra                 6                                                 Methylionone                6                                                 Hydroxycitronellal          6                                                 Oriental santal             3                                                 Patchouli                   1.5                                               Vetyveryl acetate           4.5                                               Natural degreased civet 10% sol.*                                                                         3                                                 Ciste labdanum absolute 10% sol.*                                                                         2                                                 Musk ketone                 4                                                 1,1-Dimethyl-6-tert. butyl-4-acetyl-indane                                                                0.5                                               Coumarin                    3                                                 Trichloromethylphenylcarbinyl acetate                                                                     1.5                                               Tarragon 10% sol.*          3                                                 Oak moss absolute 50% sol.* 6                                                 Benjoin resin 10% sol.*     1.5                                               Styrax cinnamic alcohol     1.5                                               Jasmine absolute            1.5                                               Rose absolute               1                                                 Cyclopentadecanolide 10% sol.*                                                                            2                                                 Methylnonylacetic aldehyde  1.5                                               ______________________________________                                         *in diethyl phthalate                                                    

By adding to 99.5 g. of this mixture 0.5 g. ** of trans- orcis-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene the composition obtainedwas more powerful than the basic composition and had an improveddiffusion as well as a very natural richness.

EXAMPLE 42 Perfume composition of the floral type

A floral type composition was prepared by mixing the followingingredients (parts by weight):

    ______________________________________                                        Decanal 10% sol.*          1                                                  Undecanal 10% sol.*        2                                                  Lauric aldehyde 10% sol.*  1                                                  Methylnonylacetic aldehyde 10% sol.*                                                                     0.5                                                Synthetic lily-of-the-valley                                                                             16.5                                               Synthetic lilac            3                                                  Synthetic rose             7                                                  Synthetic jasmine          12                                                 Bergamot                   6                                                  Tarragon 10% sol.*         3                                                  Ylang extra                9                                                  Synthetic carnation        6                                                  Methylionone               6                                                  Vetiveryl acetate          4                                                  Santalol                   2                                                  Decoloured oak moss absolute 10% sol.*                                                                   3                                                  Natural degreased civet 10% sol.*                                                                        3                                                  Lily absolute 1% sol.*     2                                                  Orange blossom absolute 10% sol.*                                                                        2                                                  Jasmine absolute           2                                                  Rose absolute              1                                                  Musk ketone                4                                                  Trichloromethylphenylcarbinyl acetate                                                                    2                                                  Colourless Tolu resin absolute 10% sol.                                                                  1.5                                                ______________________________________                                         *in diethyl phthalate                                                    

By adding to 99.5 g. of this mixture 0.5 g.** of trans- orcis-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene the composition obtainedwas more powerful than the basic composition and had an improveddiffusion as well as a very natural richness.

EXAMPLE 43 Perfume composition of the floral type

A floral type composition was prepared by mixing the followingingredients (parts by weight):

    ______________________________________                                        Rhodinol                 24                                                   l-Citronellol            21                                                   Chemically pure geraniol 12                                                   Phenylethyl alcohol      24                                                   Linalool                 2.5                                                  Farnesol                 2                                                    Eugenol                  0.5                                                  Methyleugenol            2                                                    Neryl isobutyrate        0.5                                                  Phenylethyl phenylacetate                                                                              0.5                                                  Geranyl acetate          1                                                    Guaiol acetate           0.5                                                  Citral 10% sol.*         2.5                                                  Nonanol 10% sol.*        0.5                                                  Nonanal 10% sol.*        0.5                                                  Decanal 1% sol.*         2                                                    Undecanal 10% sol.*      0.5                                                  Deterpenated geranium oil                                                                              1.5                                                  Phenylethylsalicylate    0.5                                                  ______________________________________                                         *in diethyl phthalate                                                    

By adding to 98.5 g. of this mixture 1.5 g. of trans- orcis-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene the composition obtainedwas more powerful than the basic composition and had an improveddiffusion as well as a very natural richness.

EXAMPLE 44 Perfume composition of the floral type

A floral type composition was prepared by mixing the followingingredients (parts by weight):

    ______________________________________                                        Rhodinol                 24                                                   l-Citronellol            21                                                   Chemically pure geraniol 12                                                   Phenylethyl alcohol      24                                                   Linalool                 2.5                                                  Farnesol                 2                                                    Eugenol                  0.5                                                  Methyleugenol            2                                                    Neryl isobutyrate        0.5                                                  Phenylethyl phenylacetate                                                                              0.5                                                  Geranyl acetate          1                                                    Guaiol acetate           0.5                                                  Citral 10% sol.*         2.5                                                  Nonanol 10% sol.*        0.5                                                  Nonanal 10% sol.*        0.5                                                  Decanal 1% sol.*         2                                                    Undecanal 10% sol.*      0.5                                                  Deterpenated geranium oil                                                                              1.5                                                  Phenylethylsalicylate    0.5                                                  ______________________________________                                         *in diethyl phthalate                                                    

By adding to 98.5 g. of this mixture 1.5 g. oftrans-2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene ** the compositionobtained was more powerful than the basic composition and had animproved diffusion as well as a very natural richness.

EXAMPLE 45 Perfume composition of the floral type

A floral type composition was prepared by mixing together the followingingredients (parts by weight):

    ______________________________________                                        Nonanal at 1%*           5                                                    Dodecanal at 10%*        5                                                    Undecanal at 10%*        20                                                   Oil of Coriander         20                                                   Neroli bigarade          5                                                    Styrax                   40                                                   l-Citronellol            50                                                   Phenylethyl alcohol      100                                                  Phenylacetaldehyde at 10%*                                                                             10                                                   Eugenol                  30                                                   Ylang                    80                                                   Artificial jasmine       60                                                   α-Amyl-cinnamaldehyde                                                                            40                                                   Hydroxycitronnellal      85                                                   Santal oriental          70                                                   Vetiveryl acetate        100                                                  Vetiverol                10                                                   Purified Civet at 10%*   30                                                   Musk ambrette            20                                                   Musk ketone              30                                                   Coumarin                 50                                                   Pentadecanolide at 10%*  20                                                   Bergamot                 100                                                  Total                    980                                                  ______________________________________                                         *in diethyl phthalate                                                    

By adding to 908 g. of the above mixture 20 g. oftrans-2,6,6,-trimethyl-1-crotonoyl-1,3-cyclohexadiene**, the compositionobtained had an improved floral note, a natural richness, more body anda better diffusion than the base composition.

EXAMPLE 46 Preparation of a "Tutti-Frutti" flavouring composition

A "Tutti-Frutti" flavouring composition was prepared by mixing togetherthe following ingredients (parts by weight):

    ______________________________________                                        Vanillin               20                                                     Allyl caproate         10                                                     Citral                 20                                                     Amyl butyrate          35                                                     Orange oil             45                                                     Ethyl butyrate         75                                                     Ethyl acetate          185                                                    Amyl acetate           185                                                    Lemon oil              415                                                    Total                  990                                                    ______________________________________                                    

Trans-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene (10 g.) was added to 990g. of the above mixture which was then called "test" composition. A"control" composition was prepared by adding 10 g. of additional lemonoil to 990 g. of the above mixture.

The "test" and "control" compositions were added to the food productsdescribed hereinafter in the proportions shown for 100 kg. of materialto be flavoured.

    ______________________________________                                        Cake                20 g.                                                     Pudding             5-10 g.                                                   Cooked sugar        15-20 g.                                                  ______________________________________                                    

Cooked sugar: 100 ml. of sugar syrup (prepared by dissolving 1 kg. ofsucrose in 600 ml. of water) and 20 g. of glucose were mixed togetherand slowly heated to 145°. The flavour was added and the mass wasallowed to cool and harden.

Pudding: to 500 ml. of warmed milk were added with stirring a mixture of60 g. of sucrose and 3 g. of pectin. The mixture was boiled for a fewseconds and the flavour was added. The mixture was allowed to cool.

Cake: the following ingredients were mixed together: 100 g. of vegetablemargarine, 1.5 g. of sodium chloride, 100 g. of sucrose, 2 eggs and 100g. of flour. The flavour was added and the mass was cooked for 40minutes at 180°.

The finished foodstuff samples were tested by a panel of trained personswho had to express their views about the flavour of the samples. Allmembers of the panel declared with no hesitation that the "test" sampleshad a more "round" taste than the "control" and at the same time ared-berry character.

When in the above example, 2,6,6-trimethyl-1-crotonoyl-1-cyclohexene wasreplaced by 2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene, the testsamples obtained therefrom were judged to have also a rounder taste thanthe control with however a more flowery and less fruity character thanthe test samples containing 2,6,6-trimethyl-1-crotonoyl-1-cyclohexene.

EXAMPLE 47 Preparation of a flavour composition for monastery typeliquor

A flavouring composition for monastery type liquors was prepared bymixing together the following ingredients (parts by weight):

    ______________________________________                                        Oil of Neroli          5                                                      Oil of Clove           20                                                     Oil of Cardamone       25                                                     Oil of nutmeg          25                                                     Oil of cinnamon        25                                                     Lemon oil              35                                                     Oil of sweet orange    65                                                     Angelica seed oil      75                                                     Peppermint oil         75                                                     Oil of bitter orange   200                                                    Angelica root oil      445                                                    Total                  995                                                    ______________________________________                                    

Trans-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene (5 g.) was added to 995g. of the above mixture which was then called the "test" composition. A"control" composition resulted from the addition of 5 g. of Angelicaroot oil to 995 g. of the above mixture.

A liquor base was prepared by mixing the following ingredients:

    ______________________________________                                        Alcohol 64 o.p. (96%)  325 ml.                                                wine alcohol (74%)     100 ml.                                                sugar syrup (65%)      10 ml.                                                 water                  565 ml.                                                Total                  1000 ml.                                               ______________________________________                                    

The liquor base was flavoured by adding to 100 kg. thereof 10 g. of theflavouring compositions. The finished liquor samples were tasted by apanel of tasters in the same manner as described in Example 46. Allmembers of the panel declared with no hestitation that the "test" samplehad a "rounder" taste than the "control" and at the same time a redberry character.

When in the above example, 2,6,6-trimethyl-1-crotonoyl-1-cyclohexene wasreplaced by 2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene, similarresults were experienced. However, the "test" samples were also judgedto have a more flowery and less fruity character than those containing2,6,6-trimethyl-1-crotonyl-1-cyclohexene.

EXAMPLE 48 Flavouring of foodstuffs and beverages

Trans-2,6,6-trimethyl-1-crotonoyl-1-cyclohexene was used as soleingredient to flavour the following edible goods at the doses indicated(parts by weight):

(a) Red wine, 0.2-1 ppm

(b) Raspberry syrup, 0.3-0.6 ppm (based on diluted syrup)

(c) Honey, 0.5-1 ppm

In cases (a), (b) and (c) the bouquet of the goods was markedlyimproved. In (a) the fruity side was also improved and in (c) theflowery note was furthermore enhanced. In (b) a cooked fruit note wasnoticed.

EXAMPLE 49 1,5,5,8,9-Pentamethylbicyclo[4.3.0]non-8-en-7-one

A solution of 2,6,6-trimethyl-1-[2-methyl-crotonoyl]-1-cyclohexene (1.0g.) in 10 ml. of dioxan was heated at 100° under nitrogen with acidicdiatomaceous earth (0.2 g.) until complete conversion of the startingmaterial into the bicyclic ketone. The course of the reaction wasfollowed by v.p.c. analysis of sample aliquots taken at set timeintervals. Three hours were usually required for such a reaction.

After filtration over diatomaceous earth and evaporation of the clearfiltrate, a residue was obtained which, by fractional distillation, gave1,5,5,8,9-pentamethylbicyclo[4.3.0]non-8-en-7-one in 84% yield.

n_(D) ²⁰ =1.5020; d₄ ²⁰ =0.9688

MS: M⁺ =206 (20); IR: 1655 and 1690 cm⁻¹.

NMR: 0.82 and 1.18 (6 H, 2 s); 1.18 (3 H, s); 1.91 (3 H, s); 1.54 (3 H,s) δ ppm.

EXAMPLE 50 1,4,5,5,8,9-Hexamethylbicyclo[4.3.0]non-8-en-7-one

According to the same procedure described in Example 49, a solution of2,4,6,6-tetramethyl-1-[2-methyl-crotonoyl]-1-cyclohexene (1.0 g.) in 10ml. of dioxan was heated at 100° under nitrogen with acidic diatomaceousearth (0.2 g.).

Fractional distillation gave the desired bicyclic ketone in 65% yield.

n_(D) ²⁰ =1.5042; d₄ ²⁰ =0.9766

IR: 1625 and 1690 cm⁻¹.

EXAMPLE 51 1,5,5,9-Tetramethylbicyclo[4.3.0]nona-2,8-dien-7-one

A solution of 2,6,6-trimethyl-1-crotonoyl-1,3-cyclohexadiene (1.0 g.) in10 ml. of dioxan was heated under the same conditions as described inExample 49 with acidic diatomaceous earth (0.2 g.).

The usual treatment and distillation yielded the desired bicyclicketone.

Yield ca. 80%; n_(D) ²⁰ =1.5080; d₄ ²⁰ =0.9895

MS: M⁺ =190

IR: 1620 and 1680 cm⁻¹

NMR: 0.84 and 1.13 (6 H, 2 s); 2.08 (3 H, m); 5.61 (1 H, m); 5.72 (2 H,m) δ ppm.

EXAMPLE 52 4,4,8-Trimethyl-9-methylene-bicyclo[3.3.1]nonan-6-one

A solution of 2,6,6-trimethyl-1-crotonoyl-2-cyclohexene (1.0 g.) in amixture of benzene and ether (10 ml.) was heated at ca. 80° in thepresence of a catalytic amount of a saturated solution of BF₃ in ether.The course of the reaction was followed by v.p.c. analysis. Three hourswere usually necessary for converting the starting material into thebicyclic compound.

The usual treatment followed by fractional distillation gave the desiredketone in 88% yield.

n_(D) ²⁰ =1.4955; d₄ ²⁰ =0.9642

MS: M⁺ =192 (60); IR: 1650 and 1700 cm⁻¹.

NMR: 1.02 (3 H, d, J= 7 cps); 0.84 and 0.99 (6 H, 2 s); 4.58 and 4.78 (2H, 2 m) δ ppm.

EXAMPLE 53 Preparation of a "Tutti-Frutti" flavouring composition

A "Tutti-Frutti" flavouring composition was prepared by admixing thefollowing ingredients (parts by weight):

    ______________________________________                                        Vanillin               20                                                     Allyl caproate         10                                                     Citral                 20                                                     Amyl butyrate          35                                                     Orange oil             45                                                     Ethyl butyrate         75                                                     Ethyl acetate          185                                                    Amyl acetate           185                                                    Lemon oil              400                                                    Total                  975                                                    ______________________________________                                    

1,5,5,9-Tetramethylbicyclo[4.3.0]nona-2,8-dien-7-one (25 g.) was addedto 975 g. of the above mixture which was then called "test" composition.A "control" composition was prepared by adding 25 g. of additional lemonoil to 975 g. of the above mixture.

The "test" and "control" compositions were added to the food productsdescribed hereinafter in the proportions shown for 100 kg. of materialto be flavoured.

    ______________________________________                                        Cake                20 g.                                                     Pudding             5-10 g.                                                   Cooked sugar        15-20 g.                                                  ______________________________________                                    

Cooked sugar: 100 ml. of sugar syrup (prepared by dissolving 1 kg. ofsucrose in 600 ml. of water) and 20 g. of glucose were mixed togetherand slowly heated to 145°. The flavour was added and the mass wasallowed to cool and harden.

Pudding: to 50 ml. of warmed milk were added with stirring a mixture of60 g. of sucrose and 3 g. of pectin. The mixture was boiled for a fewseconds and the flavour was added. The mixture was allowed to cool.

Cake: the following ingredients were mixed together: 100 g. of vegetablemargarine, 1.5 g. of NaCl, 100 g. of sucrose, 2 eggs and 100 g. offlour. The flavour was added and the mass was cooked for 40 minutes at180°. The finished foodstuff samples were tested by a panel of trainedpersons who had to express their views about the flavour of the samples.All members of the panel declared with no hesitation that the "test"samples had a more distinguished fruity- and woody-note than the"control" samples and at the same time a red berry character.

EXAMPLE 54 6,6-Dimethyl-2-methylene-1-crotonoylcyclohexane and1,5,5,9-tetramethylbicyclo[4.3.0]non-8-en-7-one.

H₂ O₂ (30%, 120 ml.) and 6N NaOH (30 ml.) were added to a solution ofγ-ionone (50 g.) in 3 l. of MeOH. To the reaction mixture, stirred atroom temperature for 24 h., 50 ml. of H₂ O₂ (30%) were added and thestirring was continued for 24 h. more. The addition of hydrogen peroxidewas repeated and after a total of 3 consecutive days the solution wasconcentrated in vacuo and the residue distilled.

The fractional distillation yielded 46 g. of a 55:45 mixture of 2isomeric epoxides of γ-ionone (epoxides A and B) which could beseparated by means of a spinning-band-column distillation or v.p.c.(Carbowax 20 M).

Epoxide A, b.p. 88°-9°/0.1 Torr; n_(D) ²⁰ =1.4890; d₄ ²⁰ =0.

Epoxide B, b.p. 90°-1°/0.1 Torr; m.p. 43-4°.

Epoxide A (5 g.) in 5 ml. of MeOH were added dropwise at 0° undernitrogen to a solution of 10 ml. of pure hydrazine hydrate in 5 ml. ofMeOH (1.5 h.). After 2 hours stirring, the mixture underwent the usualtreatments and gave by distillation (36% yield): cis-(isomer 8%)6,6-dimethyl-1-[1-hydroxy-2-butenyl]-2-methylen cyclohexane, thetrans-derivative of the same alcohol (isomer A, 7%) and1,5,5,9-tetramethylbicyclo[4.3.0]non-8-en 7-ol (isomer A, 80%). Thesecompounds have been separated by preparative v.p.c.

In the above procedure, by substituting epoxy A with epoxide B,6,6,-dimethyl-1[1-hydroxy-2-butenyl]methyleneycyclohexane, cis-, (isomerB, 36% the transderivative of the same alcohol (isomer B, 58%) and1,5,5,9-tetramethylbicyclo[4.3.0]non-8-en-7-ol (isomer β 2%) wereobtained.

The mixture of6,6-dimethyl-1-[1-hydroxy-2-butenyl]-2-methylenecyclohexane, form cis-,isomers A and B, and trans-, isomers A and B, was oxidised by meanschromic anhydride in the presence of pyridine [cf. J. Am. Chem. Soc. 75,422 (1953)]. A mixture of the cis- and trans-isomers of 6,6-dimethyl-2-methylene-1-croton cyclohexane were thus obtained in 70% yield. The twoproducts were separated by preparative v.p.c.

Isomer cis- (more volatile): n_(D) ²⁰ =1.4892 d₄ ²⁰ =0.9342.

Isomer trans-: n.sub.²⁰ =1.4939; d₄ ²⁰ =0.9335

According to the same procedure, a mixture of the two isomers of thebicyclic carbinol was oxidised and yielded1,5,5,9-tetramethylbicyclo[4.3.0]non-8-en-7-one. n_(D) ²⁰ =1.5028; d₄ ²⁰=0.9874.

The mixture of the 6 hydroxylic derivatives obtained by simultaneousisomerization of the 2 epoxides (isomers A and B) could be oxidisedaccording to the same procedure as used for the separated compounds. Theoxidised derivatives were obtained in a comparable yield and wereseparated by means of preparative v.p.c.

EXAMPLE 55 Preparation of a "Tutti-Frutti" flavouring composition

A "Tutti-Frutti" flavouring composition was prepared by admixing thefollowing ingredients (parts by weight):

    ______________________________________                                        Vanillin               20                                                     Allyl caproate         10                                                     Citral                 20                                                     Amyl butyrate          35                                                     Orange oil             45                                                     Ethyl butyrate         75                                                     Ethyl acetate          185                                                    Amyl acetate           185                                                    Lemon oil              400                                                    Total                  975                                                    ______________________________________                                    

1,5,5,9-Tetramethylbicyclo[4.3.0]non-8-en-7-one (25 g.) was added to 975g. of the above mixture which was then called "test" composition. A"control" composition was prepared by adding 25 g. of additional lemonoil to 975 g. of the above mixture.

The "test" and "control" compositions were added to the food productsdescribed hereinafter in the proportions shown for 100 kg. of materialto be flavoured.

    ______________________________________                                        Cake                20 g.                                                     Pudding             5-10 g.                                                   Cooked sugar        15-20 g.                                                  ______________________________________                                    

Cooked sugar: 100 ml. of sugar syrup (prepared by dissolving 1 kg. ofsucrose in 600 ml. of water) and 20 g. of glucose were mixed togetherand slowly heated to 145°. The flavour was added and the mass wasallowed to cool and harden.

Pudding: to 500 ml. of warmed milk were added with stirring a mixture of60 g. of sucrose and 3 g. of pectin. The mixture was boiled for a fewseconds and the flavour was added. The mixture was allowed to cool.

Cake: the following ingredients were mixed together: 100 g. of vegetablemargarine, 1.5 g. of NaCl, 100 g. of sucrose, 2 eggs and 100 g. offlour. The flavour was added and the mass was cooked for 40 minutes at180°.

The finished foodstuff samples were tested by a panel of trained personswho had to express their views about the flavour of the samples. Allmembers of the panel declared with no hesitation that the "test" sampleshad a more distinguished fruity- and flowery-note than the "control"samples and at the same time rounder character.

EXAMPLE 56 Perfume composition of the chypre type

A chypre type composition was prepared by mixing the followingingredients (parts by weight):

    ______________________________________                                        Bergamot                    21                                                Portugal                    0.5                                               Synthetic Neroli            1                                                 Synthetic rose              9                                                 Synthetic Jasmine           9                                                 Ylang extra                 6                                                 Methylionone                6                                                 Hydroxycitronellal          6                                                 Oriental santal             3                                                 Patchouli                   1.5                                               Vetyveryl acetate           4.5                                               Natural degreased civet 10% sol.*                                                                         3                                                 Ciste labdanum absolute 10% sol.*                                                                         2                                                 Musk ketone                 4                                                 1,1-Dimethyl-6-tert. butyl-4-acetyl-indane                                                                0.5                                               Coumarin                    3                                                 Trichloromethylphenylcarbinyl acetate                                                                     1.5                                               Tarragon 10% sol.*          3                                                 Oak moss absolute 50% sol.* 6                                                 Benjoin resin 10% sol.*     1.5                                               Styrax cinnamic alcohol     1.5                                               Jasmine absolute            1.5                                               Rose absolute               1                                                 Cyclopentadecanolide 10% sol.*                                                                            2                                                 Methylnonylacetic aldehyde  1.5                                               ______________________________________                                         *in diethyl phthalate                                                    

By adding to 99.5 g. of this mixture 0.5 g. oftrans-2,4,6,6-tetramethyl-1-crotonoyl-1-cyclohexene the compositionobtained was more powerful than the basic composition and had animproved diffusion as well as a very natural richness.

EXAMPLE 57 Perfume composition of the floral type

A floral type composition was prepared by mixing the followingingredients (parts by weight):

    ______________________________________                                        Decanal 10% sol.*          1                                                  Undecanal 10% sol.*        2                                                  Lauric aldehyde 10% sol.*  1                                                  Methylnonylacetic aldehyde 10% sol.*                                                                     0.5                                                Synthetic lily-of-the-valley                                                                             16.5                                               Synthetic lilac            3                                                  Synthetic rose             7                                                  Synthetic jasmine          12                                                 Bergamot                   6                                                  Tarragon 10% sol.*         3                                                  Ylang extra                9                                                  Synthetic carnation        6                                                  Methylionone               6                                                  Vetiveryl acetate          4                                                  Santalol                   2                                                  Decoloured oak moss absolute 10% sol.*                                                                   3                                                  Natural degreased civet 10% sol.*                                                                        3                                                  Lily absolute 1% sol.*     2                                                  Orange blossom absolute 10% sol.*                                                                        2                                                  Jasmine absolute           2                                                  Rose absolute              1                                                  Musk ketone                4                                                  Trichloromethylphenylcarbinyl acetate                                                                    2                                                  Colourless Tolu resin absolute 10% sol.                                                                  1.5                                                ______________________________________                                         *in diethyl phthalate                                                    

By adding to 99.5 g. of this mixture 0.5 g. ** of2,6,6-trimethyl-1-vinylacetyl-1-cyclohexene the composition obtained wasmore powerful than the basic composition and had an improved diffusionas well as a very natural richness.

EXAMPLE 58 Perfume composition of the floral type

A floral type composition was prepared by mixing the followingingredients (parts by weight):

    ______________________________________                                        Rhodinol                 24                                                   l-Citronellol            21                                                   Chemically pure geraniol 12                                                   Phenylethyl alcohol      24                                                   Linalool                 2.5                                                  Farnesol                 2                                                    Eugenol                  0.5                                                  Methyleugenol            2                                                    Neryl isobutyrate        0.5                                                  Phenylethyl phenylacetate                                                                              0.5                                                  Geranyl acetate          1                                                    Guaiol acetate           0.5                                                  Citral 10% sol.*         2.5                                                  Nonanol 10% sol.*        0.5                                                  Nonanal 10% sol.*        0.5                                                  Decanal 1% sol.*         2                                                    Undecanal 10% sol.*      0.5                                                  Deterpenated geranium oil                                                                              1.5                                                  Phenylethylsalicylate    0.5                                                  ______________________________________                                         *in diethyl phthalate                                                    

By adding to 98.5 g. of this mixture 1.5 g. of2,6,6-trimethyl-1-hydroxy-1-crotonoyl-2-cyclohexene the compositionobtained was more powerful than the basic composition and had animproved diffusion as well as a very natural richness.

EXAMPLE 50 Preparation of a flavour composition for monastery typeliquor

A flavouring composition for monastery type liquors was prepared bymixing together the following ingredients (parts by weight):

    ______________________________________                                        Oil of Neroli          5                                                      Oil of Clove           20                                                     Oil of Cardamone       25                                                     Oil of nutmeg          25                                                     Oil of cinnamon        25                                                     Lemon oil              35                                                     Oil of sweet orange    65                                                     Angelica seed oil      75                                                     Peppermint oil         75                                                     Oil of bitter orange   200                                                    Angelica root oil      445                                                    Total                  995                                                    ______________________________________                                    

2,4,6,6-Tetramethyl-1-trans-crotonoyl-1-cyclohexene (5 g.) was added to995 g. of the above mixture which was then called the "test"composition. A "control" composition resulted from the addition of 5 g.of Angelica root oil to 995 g. of the above mixture.

A liquor base was prepared by mixing the following ingredients:

    ______________________________________                                        Alcohol 64 o.p. (96%)  325 ml.                                                wine alcohol (74%)     100 ml.                                                sugar syrup (65%)      10 ml.                                                 water                  565 ml.                                                Total                  1000 ml.                                               ______________________________________                                    

The liquor base was flavoured by adding to 100 kg. thereof 10 g. of theflavouring compositions. The finished liquor samples were tasted by apanel of tasters in the same manner as described in Example 46. Allmembers of the panel declared with no hesitation that the "test" samplehad a "rounder" taste than the "control" and at the same time a redberry character.

When in the above example,2,4,6,6-tetramethyl-1-trans-crotonoyl-1-cyclohexene was replaced by2,4,6,6-tetramethyl-1-trans-crotonoyl-1,3-cyclohexadiene similar resultswere experienced. However, the "test" samples were also judged to have amore flowery and less fruity character than those containing2,4,6,6-tetramethyl-1-trans-crotonoyl-1-cyclohexene.

We claim:
 1. A tobacco product having incorporated therein as a taste-and flavour-modifying agent a substantially pure compound having theformula ##STR41## containing one double bond in position 2'- or 3'- ofthe acyl side-chain and either one double bond in position 1- or 2- ortwo conjugated double bonds in position 1- and 3- of the cycle, thedouble bonds being represented by dotted lines, and wherein n is zero or1, R¹, R² and R³ represent hydrogen or one of them a lower alkyl radicaland the others hydrogen, and R⁴, R⁵, R⁶ and R⁷ represent hydrogen or oneof them a lower alkyl radical and the others hydrogen.
 2. A productaccording to claim 1 wherein the lower alkyl radicals referred to aremethyl or ethyl.
 3. A product according to claim 1 wherein theincorporated compound has the formula ##STR42##